He fell asleep immediately last night. He ______ very tired.

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问题 He fell asleep immediately last night. He ______ very tired.

选项 A、must be
B、must have been
C、can be
D、could have been

答案B

解析情态动词。此句是根据结果推测原因，推测做过的事情的原因用虚拟语气的形式来表示，即：must have done表示对过去事情的肯定性推测，注意其否定形式不是在must后面加not，而是用can或could来否定，称之为否定推测。[例句] This bottle is nearly empty，you must have drunk a lot．瓶子快空了，你一定喝了不少。

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本试题收录于：大学英语三级A级题库大学英语三级分类