一道关于情态动词的英语题: -Where is Mary? -She _ in her classroom.

问题描述:

一道关于情态动词的英语题: -Where is Mary? -She _ in her classroom.
-Where is Mary? -She _ in her classroom.
A. must be B. should beC. can beD. must have been
答案是A.我想知道B为什么不对.

B这个选项的意思也是 应该在 ,但是should一般用在祈使句中,命令的语气
比如说You should do your homework quickly.你这句话是一种猜测的语气,should不适用于猜测的语气,