问题补充:
We have proved great adventurers, but we have done the greatest march ever made in the past ten years.
A. needn’t
B. may not
C. shouldn’t
D. mustn’t
答案:
A. needn’t
(答案→)B. may not
C. shouldn’t
D. mustn’t
解析:比较:needn’t have done意为“本来不必做某事”,may not have done意为“(过去)可能没有做某事”,shouldn’t have done意为“本来不应该做某事”(must表推测时不用于否定式)。根据句意,显然只能选B。