Stress and tiredness often lead to lack of______.
A. concentrate
B. concentration
C. concentrated
D. concentrator
KEY: B
Giải thích: sau giới từ là danh từ.
Dịch: Căng thẳng mà mệt mỏi thường dẫn đến mất tập trung.
Hardly any of the paintings at the gallery were for sale, _____?
English has become a second language in countries like India, Nigeria or Singapore where_______ for administration, broadcasting and education.