can't 和mustn't的用法?

问题描述:

can't 和mustn't的用法?
1.In Britain you ______ ride your bike on the pavement.
A.can't B.mustn't
2.We____forget to turn off the light before we leave.
A.mustn't B.can't

第一题选B
翻译为:在英国,你不允许在人行道上骑自行车
第二题选A
翻译为:在我们离开之前我们不能忘记关灯
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.