Read the following passage and choose A, B, C, or D to indicate the correct word or phrase that best fits each of the following blanks. Fill in the appropriate word in question 31

There are many sources of pollution in our modern world. At present, the most severe sources are acid rain, car exhaust fumes and oil spills.

Factory chimneys give (31)_________ smoke that contains sulfur dioxide and nitrogen oxide. These gases combine with the moisture in the atmosphere to (32)_________ sulfuric acid and nitric acid. When it rains, these acids dissolve in the rain and turn it acidic. Acid rain is thought to be the worst pollution problem of all. It has (33)_________ aquatic life by turning many lake into lifeless bodies of water. In these areas, there is no limestone in the rocks to neutralize the acid rain naturally. One remedy is to pump limestone into the acidic lakes. (34)_________, it is not possible to do this on a large enough scale to save all the lakes.

Car exhaust fumes contain carbon monoxide and lead which are highly poisonous. In big cities, the exhaust fumes build (35)_________ and pose a health hazard to human beings.

Pollution of the sea by oil threatens marine life. Much of the oil comes from ships that clean their fuel tanks while at sea. Offshore oil wells also discharge vast amounts of oil into the sea. Pollution of the sea can also be caused by oil spills. An oil spill may occur as a result of accidents involving oil tankers.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions

We cut down many forests. The Earth becomes hot

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions

He is very intelligent. He can solve all the problems in no time

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions

Had she read the reference books, she would have been able to finish the test

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions

“I will pay back the money, Gloria.” Said Ivan

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions

It started to rain at 2 o’clock and it is still raining

Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions

I don’t mind waiting for other ten minutes, but will you please keep me company? 

Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions

Caroline has worn her new yellow dress only once since she buys it

Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions

The police told us to refrain from touching the furniture in case they would need to look for fingerprints

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 from 35 to 42 

     Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction. 

     Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta Texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth. 

          The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space.  In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail

According to the passage, the highest amount of pheromone vapor is found _____ 

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 from 35 to 42 

     Many ants forage across the countryside in large numbers and undertake mass migrations; these activities proceed because one ant lays a trail on the ground for the others to follow. As a worker ant returns home after finding a source of food, it marks the route by intermittently touching its stinger to the ground and depositing a tiny amount of trail pheromone – a mixture of chemicals that delivers diverse messages as the context changes. These trails incorporate no directional information and may be followed by other ants in either direction. 

     Unlike some other messages, such as the one arising from a dead ant, a food trail has to be kept secret from members of other species. It is not surprising then that ant species use a wide variety of compounds as trail pheromones. Ants can be extremely sensitive to these signals. Investigators working with the trail pheromone of the leafcutter ant Atta Texana calculated that one milligram of this substance would suffice to lead a column of ants three times around Earth. 

          The vapor of the evaporating pheromone over the trail guides an ant along the way, and the ant detects this signal with receptors in its antennae. A trail pheromone will evaporate to furnish the highest concentration of vapor right over the trail, in what is called a vapor space.  In following the trail, the ant moves to the right and left, oscillating from side to side across the line of the trail itself, bringing first one and then the other antenna into the vapor space. As the ant moves to the right, its left antenna arrives in the vapor space. The signal it receives causes it to swing to the left, and the ant then pursues this new course until its right antenna reaches the vapor space. It then swings back to the right, and so weaves back and forth down the trail

The word “oscillating” in line 17 is closest in meaning to