We------ have proved great advanturers,but we have done the

We______ have proved【to be】 great 【advanturers—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是选B。句子实际可变为：We may not have proved (to be+n/adj。可省略) great adventurers,but we have done the greatest march ever made in the past ten years。句意：我们也许不是最伟大的探险家,但是过去十年中我们确实走过了最了不起的历程。needn't have done 过去本来不必做（却做了）may not have done 过去也许/可能不shouldn't have done过去本来不应该做（却做了）mustn't 禁止/不许做。表示肯定性推测判断时,要用于肯定句。否定句中常用can、could代替表示推测判断。按照语义,只有B 最合适。