Jack ____ be in the library.He is in the classroom.A.mustn't

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Jack ____ be in the library.He is in the classroom.A.mustn't B.can't 选什么呢?

选 B
1.mustn't在英语中不能用于表示推测,但是可以表示“禁止/不允许”之意.
如：You mustn't smoke here.在这里你不许抽烟.
2.can't/couldn't表示推测时,意思是“不可能...”,语气非常坚决的否定推测.
根据动作发生的时间,一般分为以下三种情况：
1）进行式（对正在发生的事情的否定推测）：can't be doing sth
如：It's already ten o'clock.My father can't be sleeping now.
2）完成式（对过去的动作的否定推测）：can't/couldn't have done sth
如：He is at schoool,so he can't/couldn't have stayed up last night.
3）一般式（对现在/将来情况的否定推测）：can't do sth
如：Your answer can't be true.
3.can/could表示推测时一般只用于否定句/疑问句,但是也可用于肯定句,只是比较少见.
其中could不表示过去式,而表示可能性较小.
如：I think the work can be completed ahead of time.我认为这项工作能提前完成.

Jack ____ be in the library.He is in the classroom.A.mustn't He isn't in the classroom .Maybe he is in the library,译为同义句, Where is Tony?He ____ in the library.A.are B.be C.must be -IS jack in the library? 请问一下1.The light is out.He ____ __ be in the classroom.A.can’ You mustn't ()(run)in the classroom. —Is Jack in the library? students mustn't----(stand)on the chair in the classroom "Where is the library?""Sorry,I ____ know" A mustn't B would You mustn't shout in the classroom.改为祈使句 mustn't,do,in,the,you,classroom,this（.）禁止在教室吵闹 You mustn't ( )( )( )in the classroom