He can't be in the classroom,I saw him go home a minute ago 我想问一下问什么不能用mustn't而用can't?

问题描述:

He can't be in the classroom,I saw him go home a minute ago 我想问一下问什么不能用mustn't而用can't?

因为表示英语中“不可能”不能用mustn't而要用can't,mustn't是不允许的意思.