Question

Since nobody gave him any help，he ________ have done the research on his own.(2013·大纲全国，26)

Since nobody gave him any help，he ________ have done the research on his own.(2013·大纲全国，26) A．can B．must C．would D．need

Answer 1

B 解析　句意为：既然没人给他帮忙，那他肯定是自己做的研究。分析主从句逻辑关系可知，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。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”。