情态动词考点
◆典型陷阱题分析◆
1. “Mike is often absent from class.” “Tell him he _____ answer for it if he goes on behaving like that.”
A. shall B. will
C. would D. can
【陷阱】几个干扰项均有可能误选。
【分析】最佳答案选A。shall 用作情态动词主要有以下两个用法：
(1) 用于疑问句中征求意见。如：
Shall I help you? 要不要我帮帮你?
Shall I open the window? 要我把窗子打开吗？
(2) 用于陈述句中表示允诺、告诫、警告、威胁、命令、规定、必然性等(可用于各类人称)。如：
You shall suffer for this. 你会为此事吃苦头的。(表威胁)
Each competitor shall wear a number. 每个参赛者要戴一个号码。(表规定)
You shall hear everything as soon as you come. 你一来就可听到所有情况了。 (表允诺)
请做以下试题(答案均选 shall)：
(1) “I promise that she _____ get a nice present on her birthday.” “Will it be a great surprise to her?”
A. should B. must
C. would D. shall
2. You _______ pay too much attention to your reading skill, as it is so important.
A. cannot B. shouldn’t
C. mustn’t D. needn’t
【陷阱】几个干扰项均有可能误选。
【分析】最佳答案选A。cannot…too…是英语中一个十分有用的表达，意为“不可能太……，无论怎样……也不算过分，越……越……”。如：
You can’t be too careful. 你越仔细越好。
You can’t praise the too much. 这本书值得大加赞扬。
We cannot work too much for the people. 我们为人民做工作是不可能做过头的。
A woman cannot have too many clothes. 女人买的衣服再多也不算多。
注：有时也可用 can never, impossible 等与too连用来表示类似意思。如：
It is impossible to get there too soon. 去那儿越早越好。
3. “Is John coming by train?” “He should, but he _____ not. He likes driving his car.”
A. must B. can
C. need D. may
【陷阱】可能误选B或C。
【分析】最佳答案为D。may 表推测，may not 意为“可能不(会坐火车来)”。句中的 He should 为 He should come by train 之省略，由于其后出现转折连词 but，说明语意有变化，再结合下文的 He likes driving his car，便可决定此题选D。注意，不能选B，因为can表示推测时通常不用肯定陈述句。
4. “I heard they went skiing in the mountains last winter.” “It ____ true because there was little snow there.”
A. may not be B. won’t be
C. couldn’t be D. mustn’t be
【陷阱】几个干扰项均有可能误选。
【分析】此题最佳答案为C，主要由下文的 because there was little snow there这一语境所决定，既然“没下什么雪”，那么“滑雪”就应是“不可能”，所以选 couldn’t be，即选C。
5. “Do you think he is lazy?” “I _____ so once, but I don’t now.”
A. may have thought B. can have thought
C. may think D. might think
答案选A。从答话人的语境可知，空格处的意思“曾经这样想过”，即对过去情况作推测，故应用“情态动词+动词完成式”；又因为 can 表推测不用于肯定句，故选A。请看类例：
Their answers are exactly the same — one of them ______ from the other.
A. must copy B. must have copied
C. should copy D. should have copied
答案选B，既然两人的答案完全一样，说明“抄袭”已经发生，故用“情态动词+动词完成式”，根据句意，应选B而不能选D。
6. You _____ be right, but I don’t think you are.
A. can
B. could
C. must
D. should
【陷阱】几个干扰项均有可能误选。
【分析】从语境上看，C、D不宜选，在剩下的A和B中，许多同学想当然地选了A，认为整个句子为现在时态，所以选can，而不选过去式 could，但是最佳答案却是B而不是A。按照英语语法，情态动词can 用于推测表示可能性时，通常只用于否定句或疑问句中，而不用于肯定句中；但 could 用于表推测时，却不仅可用于否定句和疑问句，也可用于肯定句，且此时的 could 并不是 can 的过去式，与 can 也没有时间上的差别，只是 could 比 can语气更委婉，所以答案选B。注：can 在以下特殊情况下，也可用于肯定句。一是表示抽象的可能性，即从理论上或逻辑上分析是可能的，但是实际上未必会发生。如：Anyone can make mistakes. 任何人都可能会犯错误。二是后接“be (get, seem, become)＋形容词”，表示“有时会”、“时常会”等。如：My father can be very unreasonable. 我父亲有时候很不讲道理。
◆精编陷阱题训练◆
1. “I thought you wouldn’t mind.” “Well, as a matter of fact I don’t, but you _____ me first.”
A. should ask B. should have asked
C. must ask D. must have asked
2. “I called you yesterday. A woman answered, but I didn’t recognize her voice.” “Oh, it _____ my aunt Jean.”
A. must be B. must have been
C. might be D. can have been
3. That car nearly hit me; I ______.
A. might be killed B. might have been killed
C. may be killed D. may been killed
4. It’s a very kind offer, but I really _____ accept it.
A. mustn’t B. needn’t
C. can’t D. don’t
5. The police still haven’t found her, but they’re doing all they _____.
A. may B. can
C. must D. will
6. You _____ practise the drums while the baby is sleeping.
A. needn’t B. mightn’t
C. mustn’t D. won’t
7. You _____ him the news; he knew it already.
A. needn’t tell B. needn’t have told
C. mightn’t tell D. mightn’t have told
8. As she’s not here, I suppose she _____ home.
A. must go B. must have gone
C. might go D. might be going
9. Are you still here? You ______ home hours ago.
A. should go B. should have gone
C. might go D. may have gone
10. “I called you yesterday. A woman answered, but I didn’t recognize her voice.” “Oh, it _____ my aunt Jean.”
A. must be B. must have been
C. might be D. can have been
11. I _______ have met him a long time ago. Both his name and face are very familiar.
A. may B. can
C. would D. should
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】
1. 选B，should 后接动词完成式表示“本来应该做某事，结果未做”，此处含有责备之意。
2. 选B，对过去情况的肯定推测，宜用“情态动词 + 动词完成式”，再根据句意，可确定答案为B。注：can 表示推测通常不用于肯定陈述句。
3. 选B，表示过去可能发生而实际上未发生的事，用might + 动词完成式。若只是推测过去可能已经发生的事，则可用 may [might] + 动词完成式，如 He may [might] have gone. 他可能已经走了。
4. 选C。由句意可知。
5. 选B，do all one can 意为“尽力”或“竭尽全力”。
6. 选C，mustn’t 在此相当于 can’t，且语气更强。
7. 选B，“needn’t + 动词完成式”的意思是：本来不必做某事，但实际上做了。上句意思是“你本来不必告诉他这个消息的，因为他(当时)已经知道了”。注意，句中 knew 为过去式。
8. 选B，must 后接动词完成式表示对过去情况的肯定推测，意为“一定已经做了某事”。
9. 选B，should 后接动词完成式表示“本来应该做某事，结果未做”。
10. 选B，对过去情况的肯定推测，宜用“情态动词 + 动词完成式”，再根据句意，可确定答案为B。注：can 表示推测通常不用于肯定句。
12. 选A。may have done sth 表示对过去可能发生的事进行推测，意为“可能曾经”。
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。