(2013·高考新课标全国卷Ⅱ)Since nobody gave him any help，hehave done the research on his own.A. can　

(2013·高考新课标全国卷Ⅱ)Since nobody gave him any help，he have done the research on his own.
A. can　　　　　　　
B. must
C. would
D. need

A. can　　　　　　　(答案→)B. mustC. wouldD. need解析：选B。分析主从句逻辑关系，主句是对从句表达的原因的一种猜测，must have done想必/准是/一定做过某事，符合主从句之间的逻辑关系。本题句意为“既然没人给他帮忙，那他肯定是自己做的研究”。can have done 用于疑问句或否定句中，表示对过去情况的推测；would have done表示过去将来完成时或用于虚拟语气中；need have done 通常用于否定句和疑问句中，表示“本不必做某事却做了”。

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