Mark the letter A, B, C or D on your answer sheet to indicate the word(s) CLOSET in meaning, to the underlined word(s) in each of the following questions

Mark the letter A, B, C or D on your answer sheet to indicate the word(s) CLOSET in meaning to the underlined word(s) in each of the following questions.
18. The supply is being tested for contamination.
A. population B. pollution C. combining D. containing
19. The fumes from vehicles is a contributing factor to make people cough.
A. noise B. fuel C. exhaust D. water
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.
20. Later that evening, when I was almost asleep, the sound of a crowd brought me back to full consciousness.
A afraid B. tired C. awake D. aware
21. Solar energy doesn't cause pollution and it is cheap.
A. effective B. expensive C. commercial D. possible