13. “Shall we go shopping?” “Sorry, we _______ buy anything now because none of the shops are open.”
A. mustn’t B. needn’t
C. can’t D. shouldn’t
14. They often go to the restaurants for meals. They _____ be very poor.
A. mustn’t B. can’t
C. may not D. needn’t
15. I didn’t see her in the meeting room this morning. She ______ have spoken at the meeting.
A. mustn’t B. shouldn’t
C. needn’t D. couldn’t
17. He ______ the test again, in which case, his mother will be very disappointed.
A. might fail B. must have failed
C. should fail D. could have failed
18. “Why didn’t she come to the meeting yesterday?” “I’m not so sure. She ______ ill.”
A. should be B. should have been
C. must be D. might have been
19. Why did you just sit and watch? You _______ me.
A. could help B. should help
C. could have helped D. must have helped
20. “You ______ your teacher for help. He is kind-hearted.” “Yes. A whole day _______.”
A. can ask, will waste
B. must have asked, had wasted
C. could have asked, was wasted
D. shouldn’t have asked, would be wasted
21. “Is there a flight to London this evening?” “There _______ be. I’ll phone the airport and find it out.”
A. must B. might
C. would D. can
22. “Show me your permit, please.” “Oh, it’s not in my pocket. It ______.”
A. might fall out B. could fall out
C. should have fallen out D. must have fallen out
23. “Look at these tracks. It _______ be a wolf.” “Don’t be so sure. I think it _______ be a fox.”
A. must; could B. may; might
C. need; must D. could; need
25. “Did Jim come?” “I don’t know. He _______ while I was out.”
A. might have come B. might come
C. mush have come D. should have come
【答案与解析】
13. 选C。根据上下文的语境推知。can’t 意为“不能”。
14. 选B。根据上下文的语境推知。can’t 表推测，意为“不不能”。
16. 选D。couldn’t have done sth 表示对过去情况进行推测，意为“过去不可能发生过某情况”。
17. 选A。根据下文的 will be 可知，“他考试再不及格”是将来的事，据此可排除B和D。再根据语意，排除C。
18. 选D。从时间上看，由于是昨天没来开会，所以推测他生病也应指昨天，故排除A和C。从语境上看，既然上文说 I’m not so sure，那么说明说话者对自己的推测没有很大把握，故选D。
19. 选C。根据上文的过去时态可知，此句谈的是过去的事，故排除A和C。根据语境排除D。
20. 选C。couldn’t have done sth 结构在此表示责备，指过去本来可以做某事但实际上未做。第二空填 was wasted，陈述的是过去的一事实。
21. 选B。根据下文的 I’ll phone the airport and find it out 可知，说话人对自己的推测没有很大把握，故选 might。若选A，语气太强，不合语境；若选D，不合语法习惯，因为can 表推测通常不用于肯定陈述句中。
22. 选D。既然“通行证现在不在口袋里”，那么它“掉出去”应发生在过去，故排除A和B。比较选项C和D所表示的意思，选D更恰当。
24. 选A。根据 Don’t be so sure 可知前面一空应填must。第二空填的could表示推测，虽为过去式形式，但表示现在意义，语气较委婉，它与表推测的 can 主要用于否定句和疑问句不同，它可以用于肯定陈述句。
25. 选A。根据句中有关时态可知“他来”发生在过去，故排除B;根据 I don’t know 可知选项C语气太肯定，不合适；选项D的意思是“本来应该来”，与语境不合。
