Question

---She looks very happy. She ________ have passed the exam.

---I guess so. It's not difficult after all.

1. A.
   should
2. B.
   could
3. C.
   must
4. D.
   might

Answer 1

C
句意：--她看上去很高興，她一定是通過考試了。--我認為是這樣，這次考試畢竟不很難。第一個人說她很高興。然后對她考試結(jié)果做出判斷，第二個人認可第一個人的話，并補充說考試不難，據(jù)此，我們可以看出這里是對“考試”這個過去動作做出的有把握的推測，應用must have done，而should have done表示本該做卻沒有做的動作，could/might have done表示語氣較弱的推測，故選C。