It's nearly seven o'clock. Jack ____ be here at any moment. A. must B. need C. should D. can(全国高考,95-31)
答案为 C(should)。能否选 D 呢?
我们在上一条里已经证明,肯定句中的 can 可以表示现在或将来的“可能性”。再举一个更有说服力的例证：
If it's raining tomorrow, the sports can take place indoors. 如果明天下雨,运动会可能在室内举行。
现在再来证明肯定句中的 can be 也可以表示现在或将来的“可能性”：
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Noise can be quite a problem when you're living in a flat. 如果你住在公寓里,噪音可能是一个很大的问题。
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So data of this kind can be valuable. 所以,这类资料可能是很有价值的。
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Lightning can be dangerous. 闪电可能是很危险的(闪电有时是很危险的)。
由此看来，在上面的句子里，除使用 should 之外，使用 can 也肯定是正确的。
[句意]快7点了。杰克随时都可能来这儿。
请做下面的英语试题：
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Playing with fire ____ be very dangerous. A. can B. ought C. perhaps D. have to
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“The door was open.” “It ____ open. I had locked in myself and the key was in my pocket.” A. can't be B. mustn't be C. can't have been D. mustn't have been(全国英语专业四级,92-48)