Question

【题目】 Since nobody gave him any help, he __________ have done the research on his own.

A. can

B. must

C. would

D. need

Answer 1

【答案】B

【解析】句意:既然没人给予他任何帮助，他一定是独自完成这项研究的。本题考查情态动词。must have done表示对过去情况的肯定推测，意为“一定做了”，符合语境。can表推测通常用于疑问句和否定句；would have done表示与过去事实相反的假设，通常用于虚拟语气中；need和have done连用时常用否定形式needn't have done“本没有必要做某事（而做了）”。