问题

The door is open but nobody is in. Mary______have forgotten to lock the door.
A:should
B:must
C:would
D:could;
B:must
C:would
D:could;
正确答案是:
同类题型
The socks cost _________ much _________we didn’t buy any.
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_______ that he picked up French— It was in 2010 _______ he traveled in France.
The old couple ______ for 50 years and never once have they quarreled with each other.[ ]