Mark the letter A, B, C, or D on...

Câu hỏi: 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.
There has been no discernible improvement in the noise levels since lorries were banned.

A. clear      

B. obvious 

C. thin        

D. insignificant