英语中表示请求或许可的情态动词在疑问句中，主语是第一人称，表示请求别人允许的情态动词有can, could, may, might, 且从左至右越来越正式或客气，越来越不那么常用。如：—I hear you’ve got a set of valuable Australian coin. ________ I have a look?—Yes, certainly. (北京春)A. Do B. May C. Shall D. Should【分析】答案选B。may表示请求对方允许，即：“我可以做……吗?”使用时还需注意以下4点：■表示允许或者不允许时，可用于任何人称，但不能用could, might。如：1. A left-luggage office is a place where bags ________ be left for a short time, especially at a railway station. (全国卷)A. should B. canC. must D. will【分析】答案选B。can表示“可以”。should(应该), must(必须), will(愿意)均不符语境。2. —Will you stay for lunch?—Sorry, ________. My brother is coming to see me. (全国卷)A. I mustn’t B. I can’t C. I needn’t D. I won’t【分析】答案选B。can’t不可以。家兄要来这一客观情况“不允许”我在这吃饭。mustn’t 语气太强；needn’t(不必)和won’t(不愿)均不得体。3. —Could I borrow your dictionary? —Yes, of course you ________. (全国卷)A. might B. will C. can D. should【分析】答案选C。允许别人做某事时，不可用could, might，可用can, may。表示不允许别人做某事时，可以说No, you can’t / may not / mustn’t. (不可以)，还可以用I’m afraid not. (恐怕不行)，I’d rather you didn’t. (我希望你不)，Certainly not. (当然不行)等来回答。礼貌地拒绝对方的请求时，还可以伴以某种说明。如I’m afraid you can’t because…■当迫切要求得到肯定答复时，往往用can’t和couldn’t来代替can和could。但不用或很少用May I not…? Mayn’t I…? Might I not…? 如：—Mum, I’ve been studying English since 8 o’clock. ________ I go out and play with Tom for a while?—No, I’m afraid not. Besides it’s raining outside now. (辽宁卷)A. Can’t B. Wouldn’tC. May not D. Won’t【分析】答案选A。迫切要求得到肯定答复用Can’t I…? 另外，可用Won’t / Wouldn’t / Will / Would you…?来询问对方是否愿意做某事，但却没有Won’t / Wouldn’t / Will / Would I…?的说法。■表示客气的请求的方式还有：Do you think I could / might use your phone? 或I wonder if I could / might use your phone?等。■主语是第二人称，可用Can / Could you…?但不说May / Might you…?如： How ________ you say that you really understand the whole story if you have covered only a part of the article? (上海卷)A. can B. mustC. need D. may【分析】答案选A。can在疑问句中，表示疑惑、怀疑，可译作“可以”。答案B和C意义不通，答案D的may，不能用于may you…?

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