21. If you ______ go, at least wait until the storm is over.
A. can B. may C. must D. will
【答案】C
【解析】句意：如果你坚持要走，至少也要等暴风雨停了再走。must表示一定要，坚持要（表示主张），符合语境。其他选项语气较弱，均不符合句子中有暴风雨必须要走的语气。
22. What are you doing out of bed, Tom? You're to be asleep. ,
A. supposed B. known C. thought D. considered
【答案】A
【解析】句意：汤姆，你从床上下来，在做什么？你本来早应该睡着了。be supposed to do sth.“被期望或被要求（按规则、惯例等）做某事”，又如：They were supposed to be here an hour ago．他们应该在一个小时以前到达这儿。B项know“知道，了解”，C项thought“认为”；D项“认为，考虑”，均不符合题意。
