--- Guess what! I have got A for my term paper.
--- Great! You read widely and put a lot of work into it.
A. must
B. should
C. must have
D. should have
网友回答
A. must
B. should
(答案→)C. must have
D. should have
解析：情态动词表推测的用法。说话人听到对方说 “I have got A for my term paper”，据此来推断对方一定是读了好多书，花费了大量的心血。 “must have+过去分词”表示对过去发生事情较有把握的推测；“should have+过去分词”则表示过去应该做，但实际上没有，与题意不符。