—What a pity! Their experiment is a fail

问题选择题

—What a pity! Their experiment is a failure.

—They ________ better under more favorable conditions.

A．should have done

B．could have done

C．must have done

D．may have done

答案

题目分析：句意：--真遗憾,他们的实验是一个失败.—在更加有利的条件下他们本应该做的更好。这里under more favorable conditions.是一个隐含的虚拟语气,相当于if they had been under more favorable conditions.说明是和过去相反的虚拟条件句,所以主句是could have done“过去本可以做的更好”，所以选B。