Đề thi giữa kì 2 Tiếng Anh 12 có đáp án (Đề 1)
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4753 lượt thi
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35 câu hỏi
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45 phút
Danh sách câu hỏi
Câu 1:
Mark the letter A, B, C or D on your answer sheet to indicate the most suitable respone to complete each of the following exchanges.
Ann: “Passing a university entrance exam is not difficult.” - John: “_____.”
Đáp án D.
Câu 2:
Mark the letter A, B, C or D on your answer sheet to indicate the most suitable respone to complete each of the following exchanges.
Mary: “Our team has just won that English Competition.” - Anne: “_____”
Đáp án B.
Câu 3:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Facebook is a for-profit online social media and social networking service. The Facebook website was launched on February 4th, 2004 by Mark Zuckerberg, along with fellow Harvard College students and roommates. Since 2006, anyone age 13 and older has been allowed to become a registered user of Facebook though variations exist in minimum age requirement, depending on applicable local laws.
Over 25 million people in the Uk use Facebook. That’s 45% of population! And on average, each user spends over six hours a month on Facebook. Though not the highest this is a considerable number. Is Facebook is a dangerous obsession or just harmless fun? Seventeen- year-old Bethan has written on her blog about what it was like to stop using Facebook.
I think I am a Facebook addict. I log on to Facebook everyday to chat to my friends real friends and loads of online friends. Sometimes I have ten conversations going at the same time. I upload photos and update my Facebook profile all the time. But recently I’ve started to feel worried if I am offline for more than a few hours. And then last week I forgot to meet a real friend because I was online! I’ve realised I could have a problem. So I’ve decided to give it up for a while.
I found it really hard. Facebook and my friends demanded to know why I had left. I spent the first few evenings wondering what everyone was chatting on Facebook. I even phoned a couple of friends to find out.
The fourth night I wasn’t quite so bad. I actually concentrated on my homework better and I had more time to watch my TV programmes. And I spoke to my friends during the day at school. At the end of the first week, I reactivated my account, I think Facebook is fun and it’s useful for posting messages to friends and sharing photos. But I’ll try not to spend so much time on it in the future.
Question: Which of the following is NOT true about Facebook users in UK?
Đáp án C.
Câu 4:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Facebook is a for-profit online social media and social networking service. The Facebook website was launched on February 4th, 2004 by Mark Zuckerberg, along with fellow Harvard College students and roommates. Since 2006, anyone age 13 and older has been allowed to become a registered user of Facebook though variations exist in minimum age requirement, depending on applicable local laws.
Over 25 million people in the Uk use Facebook. That’s 45% of population! And on average, each user spends over six hours a month on Facebook. Though not the highest this is a considerable number. Is Facebook is a dangerous obsession or just harmless fun? Seventeen- year-old Bethan has written on her blog about what it was like to stop using Facebook.
I think I am a Facebook addict. I log on to Facebook everyday to chat to my friends real friends and loads of online friends. Sometimes I have ten conversations going at the same time. I upload photos and update my Facebook profile all the time. But recently I’ve started to feel worried if I am offline for more than a few hours. And then last week I forgot to meet a real friend because I was online! I’ve realised I could have a problem. So I’ve decided to give it up for a while.
I found it really hard. Facebook and my friends demanded to know why I had left. I spent the first few evenings wondering what everyone was chatting on Facebook. I even phoned a couple of friends to find out.
The fourth night I wasn’t quite so bad. I actually concentrated on my homework better and I had more time to watch my TV programmes. And I spoke to my friends during the day at school. At the end of the first week, I reactivated my account, I think Facebook is fun and it’s useful for posting messages to friends and sharing photos. But I’ll try not to spend so much time on it in the future.
Question: The highlight word “it” in the passage refers to_____.
Đáp án B.
Câu 5:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Facebook is a for-profit online social media and social networking service. The Facebook website was launched on February 4th, 2004 by Mark Zuckerberg, along with fellow Harvard College students and roommates. Since 2006, anyone age 13 and older has been allowed to become a registered user of Facebook though variations exist in minimum age requirement, depending on applicable local laws.
Over 25 million people in the Uk use Facebook. That’s 45% of population! And on average, each user spends over six hours a month on Facebook. Though not the highest this is a considerable number. Is Facebook is a dangerous obsession or just harmless fun? Seventeen- year-old Bethan has written on her blog about what it was like to stop using Facebook.
I think I am a Facebook addict. I log on to Facebook everyday to chat to my friends real friends and loads of online friends. Sometimes I have ten conversations going at the same time. I upload photos and update my Facebook profile all the time. But recently I’ve started to feel worried if I am offline for more than a few hours. And then last week I forgot to meet a real friend because I was online! I’ve realised I could have a problem. So I’ve decided to give it up for a while.
I found it really hard. Facebook and my friends demanded to know why I had left. I spent the first few evenings wondering what everyone was chatting on Facebook. I even phoned a couple of friends to find out.
The fourth night I wasn’t quite so bad. I actually concentrated on my homework better and I had more time to watch my TV programmes. And I spoke to my friends during the day at school. At the end of the first week, I reactivated my account, I think Facebook is fun and it’s useful for posting messages to friends and sharing photos. But I’ll try not to spend so much time on it in the future.
Question: Facebook _______.
Đáp án C.
Câu 6:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Facebook is a for-profit online social media and social networking service. The Facebook website was launched on February 4th, 2004 by Mark Zuckerberg, along with fellow Harvard College students and roommates. Since 2006, anyone age 13 and older has been allowed to become a registered user of Facebook though variations exist in minimum age requirement, depending on applicable local laws.
Over 25 million people in the Uk use Facebook. That’s 45% of population! And on average, each user spends over six hours a month on Facebook. Though not the highest this is a considerable number. Is Facebook is a dangerous obsession or just harmless fun? Seventeen- year-old Bethan has written on her blog about what it was like to stop using Facebook.
I think I am a Facebook addict. I log on to Facebook everyday to chat to my friends real friends and loads of online friends. Sometimes I have ten conversations going at the same time. I upload photos and update my Facebook profile all the time. But recently I’ve started to feel worried if I am offline for more than a few hours. And then last week I forgot to meet a real friend because I was online! I’ve realised I could have a problem. So I’ve decided to give it up for a while.
I found it really hard. Facebook and my friends demanded to know why I had left. I spent the first few evenings wondering what everyone was chatting on Facebook. I even phoned a couple of friends to find out.
The fourth night I wasn’t quite so bad. I actually concentrated on my homework better and I had more time to watch my TV programmes. And I spoke to my friends during the day at school. At the end of the first week, I reactivated my account, I think Facebook is fun and it’s useful for posting messages to friends and sharing photos. But I’ll try not to spend so much time on it in the future.
Question: Which of the following is NOT the thing Bethan does as a Facebook addict?
Đáp án D.
Câu 7:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Facebook is a for-profit online social media and social networking service. The Facebook website was launched on February 4th, 2004 by Mark Zuckerberg, along with fellow Harvard College students and roommates. Since 2006, anyone age 13 and older has been allowed to become a registered user of Facebook though variations exist in minimum age requirement, depending on applicable local laws.
Over 25 million people in the Uk use Facebook. That’s 45% of population! And on average, each user spends over six hours a month on Facebook. Though not the highest this is a considerable number. Is Facebook is a dangerous obsession or just harmless fun? Seventeen- year-old Bethan has written on her blog about what it was like to stop using Facebook.
I think I am a Facebook addict. I log on to Facebook everyday to chat to my friends real friends and loads of online friends. Sometimes I have ten conversations going at the same time. I upload photos and update my Facebook profile all the time. But recently I’ve started to feel worried if I am offline for more than a few hours. And then last week I forgot to meet a real friend because I was online! I’ve realised I could have a problem. So I’ve decided to give it up for a while.
I found it really hard. Facebook and my friends demanded to know why I had left. I spent the first few evenings wondering what everyone was chatting on Facebook. I even phoned a couple of friends to find out.
The fourth night I wasn’t quite so bad. I actually concentrated on my homework better and I had more time to watch my TV programmes. And I spoke to my friends during the day at school. At the end of the first week, I reactivated my account, I think Facebook is fun and it’s useful for posting messages to friends and sharing photos. But I’ll try not to spend so much time on it in the future.
Question: The word “applicable” in paragraph 1 is closest in meaning to_____.
Đáp án C.
Câu 8:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Facebook is a for-profit online social media and social networking service. The Facebook website was launched on February 4th, 2004 by Mark Zuckerberg, along with fellow Harvard College students and roommates. Since 2006, anyone age 13 and older has been allowed to become a registered user of Facebook though variations exist in minimum age requirement, depending on applicable local laws.
Over 25 million people in the Uk use Facebook. That’s 45% of population! And on average, each user spends over six hours a month on Facebook. Though not the highest this is a considerable number. Is Facebook is a dangerous obsession or just harmless fun? Seventeen- year-old Bethan has written on her blog about what it was like to stop using Facebook.
I think I am a Facebook addict. I log on to Facebook everyday to chat to my friends real friends and loads of online friends. Sometimes I have ten conversations going at the same time. I upload photos and update my Facebook profile all the time. But recently I’ve started to feel worried if I am offline for more than a few hours. And then last week I forgot to meet a real friend because I was online! I’ve realised I could have a problem. So I’ve decided to give it up for a while.
I found it really hard. Facebook and my friends demanded to know why I had left. I spent the first few evenings wondering what everyone was chatting on Facebook. I even phoned a couple of friends to find out.
The fourth night I wasn’t quite so bad. I actually concentrated on my homework better and I had more time to watch my TV programmes. And I spoke to my friends during the day at school. At the end of the first week, I reactivated my account, I think Facebook is fun and it’s useful for posting messages to friends and sharing photos. But I’ll try not to spend so much time on it in the future.
Question: What does Bethan conclude about Facebook?
Đáp án D.
Câu 9:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Facebook is a for-profit online social media and social networking service. The Facebook website was launched on February 4th, 2004 by Mark Zuckerberg, along with fellow Harvard College students and roommates. Since 2006, anyone age 13 and older has been allowed to become a registered user of Facebook though variations exist in minimum age requirement, depending on applicable local laws.
Over 25 million people in the Uk use Facebook. That’s 45% of population! And on average, each user spends over six hours a month on Facebook. Though not the highest this is a considerable number. Is Facebook is a dangerous obsession or just harmless fun? Seventeen- year-old Bethan has written on her blog about what it was like to stop using Facebook.
I think I am a Facebook addict. I log on to Facebook everyday to chat to my friends real friends and loads of online friends. Sometimes I have ten conversations going at the same time. I upload photos and update my Facebook profile all the time. But recently I’ve started to feel worried if I am offline for more than a few hours. And then last week I forgot to meet a real friend because I was online! I’ve realised I could have a problem. So I’ve decided to give it up for a while.
I found it really hard. Facebook and my friends demanded to know why I had left. I spent the first few evenings wondering what everyone was chatting on Facebook. I even phoned a couple of friends to find out.
The fourth night I wasn’t quite so bad. I actually concentrated on my homework better and I had more time to watch my TV programmes. And I spoke to my friends during the day at school. At the end of the first week, I reactivated my account, I think Facebook is fun and it’s useful for posting messages to friends and sharing photos. But I’ll try not to spend so much time on it in the future.
Question: What happened to make Bethan decide to quit Facebook for a while?
Đáp án A.
Câu 10:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Facebook is a for-profit online social media and social networking service. The Facebook website was launched on February 4th, 2004 by Mark Zuckerberg, along with fellow Harvard College students and roommates. Since 2006, anyone age 13 and older has been allowed to become a registered user of Facebook though variations exist in minimum age requirement, depending on applicable local laws.
Over 25 million people in the Uk use Facebook. That’s 45% of population! And on average, each user spends over six hours a month on Facebook. Though not the highest this is a considerable number. Is Facebook is a dangerous obsession or just harmless fun? Seventeen- year-old Bethan has written on her blog about what it was like to stop using Facebook.
I think I am a Facebook addict. I log on to Facebook everyday to chat to my friends real friends and loads of online friends. Sometimes I have ten conversations going at the same time. I upload photos and update my Facebook profile all the time. But recently I’ve started to feel worried if I am offline for more than a few hours. And then last week I forgot to meet a real friend because I was online! I’ve realised I could have a problem. So I’ve decided to give it up for a while.
I found it really hard. Facebook and my friends demanded to know why I had left. I spent the first few evenings wondering what everyone was chatting on Facebook. I even phoned a couple of friends to find out.
The fourth night I wasn’t quite so bad. I actually concentrated on my homework better and I had more time to watch my TV programmes. And I spoke to my friends during the day at school. At the end of the first week, I reactivated my account, I think Facebook is fun and it’s useful for posting messages to friends and sharing photos. But I’ll try not to spend so much time on it in the future.
Question: When she decided to give up Facebook_____.
Đáp án C.
Câu 11:
Mark the letter A, B, C or D on your answer sheet to indicate the word that differs from the three in the position of primary stress in each of the following questions.
Đáp án C.
Câu 12:
Mark the letter A, B, C or D on your answer sheet to indicate the word that differs from the three in the position of primary stress in each of the following questions.
Đáp án C.
Câu 13:
Mark the letter A, B, C or D on your answer sheet to indicate the best answer of each following questions.
“You stole my best cassette, Bob.” said Willy.
Đáp án D.
Câu 14:
Mark the letter A, B, C or D on your answer sheet to indicate the best answer of each following questions.
If you don’t have his number, you can’t phone him.
Đáp án B.
Câu 15:
Mark the letter A, B, C or D on your answer sheet to indicate the best answer of each following questions.
There are many things I want for Christmas. Some are clothes, toys and money.
Đáp án D.
Câu 16:
Mark the letter A, B, C or D on your answer sheet to indicate the best answer of each following questions.
Tom and May never help at home. The reason is because their mother never asks to.
Đáp án B.
Câu 17:
Mark the letter A, B, C or D on your answer sheet to indicate the best answer of each following questions.
Mr Pike is repairing the refrigerator in the kitchen at the moment.
Đáp án C.
Câu 18:
Mark the letter A, B, C, D on your answer sheet to indicate the word whose underlined part differs from that of the other three in pronunciation in each of the following questions:
Đáp án A.
Câu 19:
Mark the letter A, B, C, D on your answer sheet to indicate the word whose underlined part differs from that of the other three in pronunciation in each of the following questions:
Đáp án C.
Câu 20:
Mark the letter A, B, C, D on your answer sheet to indicate the underlined part that needs correction in each of the following questions:
A lot of rice were exported to France last year.
Đáp án A.
Câu 21:
Mark the letter A, B, C, D on your answer sheet to indicate the underlined part that needs correction in each of the following questions:
If you think carefully before making your decision, you will avoid to get into trouble later.
Đáp án A.
Câu 22:
Mark the letter A, B, C, D on your answer sheet to indicate the underlined part that needs correction in each of the following questions:
The books writing by Mark Twain are very popular in the world.
Đáp án D.
Câu 23:
Mark the letter A, B, C or D on your answer sheet to indicate the word or phrase that is CLOSEST in meaning to the underlined part in each of the following.
The teacher gave some suggestions on what would come out for the examination.
Đáp án D.
Câu 24:
Mark the letter A, B, C or D on your answer sheet to indicate the word or phrase that is CLOSEST in meaning to the underlined part in each of the following.
When being interviewed, you should concentrate on what the interviewer is saying or asking you.
Đáp án D.
Câu 25:
Mark the letter A, B, C or D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions.
A chronic lack of sleep may make us irritable and reduce our motivation to work.
Đáp án A.
Câu 26:
Mark the letter A, B, C or D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions.
He had never experienced such discourtesy towards the president as it occurred at annual meeting in May.
Đáp án D.
Câu 27:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrases that best fits each of the numbered blanks.
Most educational specialists believe that early schooling should provide children with an (27)_____ of their own abilities and the self-confidence to use their abilities. One approach recognised by many (28)______ as promoting these qualities is the Montessori method, first practised by Maria Montessori of Italy in the early 1900s. Nancy McCormick Rambusch is credited with (29) ______ the method in the United States, where today there are over 400 Montessori schools.
The method helps children learn for themselves by (30) ______ them with instructional materials and tasks that facilitate acts of discovery and manipulation. Through such exploration, children develop their sense of touch and learn (31)______ to do everyday tasks without adult assistance. Other benefits include improvement in language skills, and acquaintance with elements of science, music, and art.
Question 27:
Đáp án A.
Câu 28:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrases that best fits each of the numbered blanks.
Most educational specialists believe that early schooling should provide children with an (27)_____ of their own abilities and the self-confidence to use their abilities. One approach recognised by many (28)______ as promoting these qualities is the Montessori method, first practised by Maria Montessori of Italy in the early 1900s. Nancy McCormick Rambusch is credited with (29) ______ the method in the United States, where today there are over 400 Montessori schools.
The method helps children learn for themselves by (30) ______ them with instructional materials and tasks that facilitate acts of discovery and manipulation. Through such exploration, children develop their sense of touch and learn (31)______ to do everyday tasks without adult assistance. Other benefits include improvement in language skills, and acquaintance with elements of science, music, and art.
Question 28:
Đáp án D.
Câu 29:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrases that best fits each of the numbered blanks.
Most educational specialists believe that early schooling should provide children with an (27)_____ of their own abilities and the self-confidence to use their abilities. One approach recognised by many (28)______ as promoting these qualities is the Montessori method, first practised by Maria Montessori of Italy in the early 1900s. Nancy McCormick Rambusch is credited with (29) ______ the method in the United States, where today there are over 400 Montessori schools.
The method helps children learn for themselves by (30) ______ them with instructional materials and tasks that facilitate acts of discovery and manipulation. Through such exploration, children develop their sense of touch and learn (31)______ to do everyday tasks without adult assistance. Other benefits include improvement in language skills, and acquaintance with elements of science, music, and art.
Question 29:
Đáp án D.
Câu 30:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrases that best fits each of the numbered blanks.
Most educational specialists believe that early schooling should provide children with an (27)_____ of their own abilities and the self-confidence to use their abilities. One approach recognised by many (28)______ as promoting these qualities is the Montessori method, first practised by Maria Montessori of Italy in the early 1900s. Nancy McCormick Rambusch is credited with (29) ______ the method in the United States, where today there are over 400 Montessori schools.
The method helps children learn for themselves by (30) ______ them with instructional materials and tasks that facilitate acts of discovery and manipulation. Through such exploration, children develop their sense of touch and learn (31)______ to do everyday tasks without adult assistance. Other benefits include improvement in language skills, and acquaintance with elements of science, music, and art.
Question 30:
Đáp án D.
Câu 31:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrases that best fits each of the numbered blanks.
Most educational specialists believe that early schooling should provide children with an (27)_____ of their own abilities and the self-confidence to use their abilities. One approach recognised by many (28)______ as promoting these qualities is the Montessori method, first practised by Maria Montessori of Italy in the early 1900s. Nancy McCormick Rambusch is credited with (29) ______ the method in the United States, where today there are over 400 Montessori schools.
The method helps children learn for themselves by (30) ______ them with instructional materials and tasks that facilitate acts of discovery and manipulation. Through such exploration, children develop their sense of touch and learn (31)______ to do everyday tasks without adult assistance. Other benefits include improvement in language skills, and acquaintance with elements of science, music, and art.
Question 31:
Đáp án A.
Câu 32:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
It’s a sound you will probably never hear, a sickened tree sending out a distress signal. But a group of scientists has heard the cries, and they think some insects also hear the trees and are drawn to them like vulture to a dying animal. Researchers with the US Department of Agriculture’s Forest Service fastened sensors to the bark of drought-stricken trees clearly heard distress calls. According to one of the scientists, most parched trees transmit their plight in the 50-hertz to 50kilohertz range. (The unaided human ear can detect no more than 20 kilohertz). Red oak, maple, white pine, and birch all make slightly different sounds in the form of vibrations at the surface of the wood.
The scientists think that the vibrations are created when the water columns inside tubes that run along the length of the tree break, a result of too little water following through them.
These fractured columns send out distinctive vibration patterns. Because some insects communicate at ultrasonic frequencies, they may pick up the trees' vibration and attack the weakened trees. Researchers are now running tests with potted trees that have been deprived of water to see if the sound is what attracts the insects. “Water-stressed trees also smell differently from other trees, and they experience thermal changes, so insects could be responding to something other than sound”, one scientist said.
Question: All the following are mentioned as possible factors in drawing insects to weakened trees EXCEPT______.
Đáp án C.
Câu 33:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
It’s a sound you will probably never hear, a sickened tree sending out a distress signal. But a group of scientists has heard the cries, and they think some insects also hear the trees and are drawn to them like vulture to a dying animal. Researchers with the US Department of Agriculture’s Forest Service fastened sensors to the bark of drought-stricken trees clearly heard distress calls. According to one of the scientists, most parched trees transmit their plight in the 50-hertz to 50kilohertz range. (The unaided human ear can detect no more than 20 kilohertz). Red oak, maple, white pine, and birch all make slightly different sounds in the form of vibrations at the surface of the wood.
The scientists think that the vibrations are created when the water columns inside tubes that run along the length of the tree break, a result of too little water following through them.
These fractured columns send out distinctive vibration patterns. Because some insects communicate at ultrasonic frequencies, they may pick up the trees' vibration and attack the weakened trees. Researchers are now running tests with potted trees that have been deprived of water to see if the sound is what attracts the insects. “Water-stressed trees also smell differently from other trees, and they experience thermal changes, so insects could be responding to something other than sound”, one scientist said.
Question: It can be inferred from the passage that research concerning the distress signals of trees______.
Đáp án D.
Câu 34:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
It’s a sound you will probably never hear, a sickened tree sending out a distress signal. But a group of scientists has heard the cries, and they think some insects also hear the trees and are drawn to them like vulture to a dying animal. Researchers with the US Department of Agriculture’s Forest Service fastened sensors to the bark of drought-stricken trees clearly heard distress calls. According to one of the scientists, most parched trees transmit their plight in the 50-hertz to 50kilohertz range. (The unaided human ear can detect no more than 20 kilohertz). Red oak, maple, white pine, and birch all make slightly different sounds in the form of vibrations at the surface of the wood.
The scientists think that the vibrations are created when the water columns inside tubes that run along the length of the tree break, a result of too little water following through them.
These fractured columns send out distinctive vibration patterns. Because some insects communicate at ultrasonic frequencies, they may pick up the trees' vibration and attack the weakened trees. Researchers are now running tests with potted trees that have been deprived of water to see if the sound is what attracts the insects. “Water-stressed trees also smell differently from other trees, and they experience thermal changes, so insects could be responding to something other than sound”, one scientist said.
Question: It can be inferred from the passage that research concerning the distress signals of trees______.Which of the following could be considered a cause of the distress signals of trees?
Đáp án D.
Câu 35:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
It’s a sound you will probably never hear, a sickened tree sending out a distress signal. But a group of scientists has heard the cries, and they think some insects also hear the trees and are drawn to them like vulture to a dying animal. Researchers with the US Department of Agriculture’s Forest Service fastened sensors to the bark of drought-stricken trees clearly heard distress calls. According to one of the scientists, most parched trees transmit their plight in the 50-hertz to 50kilohertz range. (The unaided human ear can detect no more than 20 kilohertz). Red oak, maple, white pine, and birch all make slightly different sounds in the form of vibrations at the surface of the wood.
The scientists think that the vibrations are created when the water columns inside tubes that run along the length of the tree break, a result of too little water following through them.
These fractured columns send out distinctive vibration patterns. Because some insects communicate at ultrasonic frequencies, they may pick up the trees' vibration and attack the weakened trees. Researchers are now running tests with potted trees that have been deprived of water to see if the sound is what attracts the insects. “Water-stressed trees also smell differently from other trees, and they experience thermal changes, so insects could be responding to something other than sound”, one scientist said.
Question: Which of the following is the main topic of the passage?
Đáp án D.