Someone left the door of our classroom unlocked yesterday It ____Bruce.He was the last to leave
问题描述：
Someone left the door of our classroom unlocked yesterday It ____Bruce.He was the last to leave
school
Ashould be B must be C must have been D should have been
答
B
整个句子翻译为有人离开教室的时候没有锁门,一定是Bruce ,他是最后一个离开教室的.
B选项must be 表示肯定猜测（英文中的固定用法