语法课:情态动词

you mustn't.

b.can与be able to:can表示有能力做某事,be able to表示通过努力、克服困难做成某事。如:

Although his leg was hurt, he was able to swim to the bank,

c.can't和mustn't;can't多表示\没能力''或否定的推测,也可表示\不可以,不允许\等含义,而mustn't 表达\禁止,不允许\含义时更

常用,而且语气更强。如: Man can't live without air.

He can't be that foolish. Students mustn't smoke. d. can/could用于否定句或疑问句,表示\不可能是(在)……\或\可能是(在)……吗\。

You can't be serious. =You must be kidding/ joking.

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