The key __ be Peter's.His is still in the lock.A,can't B.mustn't

问题描述:

The key __ be Peter's.His is still in the lock.A,can't B.mustn't

A
A表示不可能,表示肯定用MUST
例如:The key must be Peter's.表肯定
B表示禁止,不允许,表否定要用can't