Question

The scientist __________ the experiment for half a year, but he _______ yet.

A. made; didn’t succeed
B. made; hasn’t succeeded
C. was making; didn’t succeed
D. has been making; hasn’t succeeded

Answer 1

答案D
考查时态。根据for half a year可知应该使用完成时，再根据句意可知完成进行时符合句子的意思。Yet也和完成时连用。结合句意可知D正确。句意：半年来那位科学家一直在做那个实验，但他还没有成功。