must 作为情态动词的用法问题?试比较以下的句子有何不同:句一:He must have been in his office last night.句二:You must hand in the report immediately.

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must 作为情态动词的用法问题?试比较以下的句子有何不同:句一:He must have been in his office last night.句二:You must hand in the report immediately.

must 作为情态动词的用法问题?试比较以下的句子有何不同:句一:He must have been in his office last night.句二:You must hand in the report immediately.
must 作为情态动词的用法问题?
试比较以下的句子有何不同:
句一:
He must have been in his office last night.
句二:
You must hand in the report immediately.

must 作为情态动词的用法问题?试比较以下的句子有何不同:句一:He must have been in his office last night.句二:You must hand in the report immediately.
你列举的这两组句子中的must就是其做情态动词的用法,但是它们之间有所不同.
试分析如下:
第一句中的must 除了表示主观意愿的"必须"以外,还可以表示"推测",语气十分肯定.而第二句中的"must"则表示"必须",含有命令的意味,是情态动词的一种用法,除了"must"以外,其它情态动词can/could,may/might等都有类似的用法

He must have been in his office last night.
他昨夜一定去过办公室. (肯定句) must表示一定
You must hand in the report immediately.
你必须马上上交汇报. (祈使句) must表示必须

第一句表示猜测翻译“一定”,这里是对过去情况的判断,不做情态动词用,有虚拟语气。
第二句是情态动词,翻译成“必须”,这里表示将来

must do sth 1句是表肯定,2句表命令