He may not have finished the work. (此句中用might 语气较更弱)
三. must 和 have to 的用法
1. 表示必须、必要。
You must come on time.
当must 引出的问句时, 若是否定的回答,不能用mustnt,而用neednt或dont have to.
Must we hand in our exercise our books today?
Yes, you must. (No, neednt/you dont have to.)
2. must be + 表语的结构表示推测,它的否定或疑问形式用can 代替must。如:
He must be our new teacher.
Can he be our new teacher? He cant be our new teacher.
※ 附加疑问句要和谓语动词实际时态一致。如:
He must be our new teacher, isnt he?
3. must + have +done 的结构常用在肯定句中,表示对过去或完成的情况推测,它的否定或疑问形式也用can代替must.
He must have finished his work.
※ 附加疑问句也要和谓语动词实际时态一致。如:
He must have finished his work already, hasnt he?
He must have finished his work at four yesterday, didnt he?
4. have to 的含义与must相似,两者往往可以互换使用,但have to有各种形式,随have的变化而定,must 与have to有下列几点不同:
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