英语虚拟语气

Question

I think he must have been very busy last might ,Otherwise he ______to the party. 为什么是 Would have come而不是would come

Answer 1

用would come 与将来相反
舞会是发生在昨天，没有来舞会也是发生在昨天，所以与过去相反，故用 Would have come

虚拟语气在条件句中的用法：

1.与现在事实相反
主句时态：Should\would\could\might+do（动词原形）
从句时态：过去式（be动词各人称都用were）
例句：If I were you, I should \would make full use of my time to study.

2.与过去事实相反
主句时态：Should\would\could\might+have done（动词过去分词）
从句时态：Had+done(过去分词)
例句：If you had come earlier, you would have met him.

3.与将来事实相反
主句时态： Should\would\could\might+do（动词原形）
从句时态：（可以使用下列其中之一时态）
a. 过去式（be动词各人称都用were）
b. should+动词原形
c. were to +动词原形
例句：If it rained \should rain\were to rain tomorrow, the crops would be saved.

Answer 2

此句涉及到一个含蓄条件句的用法：
含蓄条件句:在特定的上下文或一目了然的情况下，if条件句可以省略，或使用介词短语、副词或非谓语动词等形式来代替if条件句，这种虚拟语气表达形式叫做含蓄条件句。
此句中otherwise作副词暗示条件."otherwise "相当于 If he had not been busy last night 表对过去的虚拟,主句用would have come 与从句相对应的形式。

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Answer 3

must have done 是对过去发生的事的肯定推测，后面的last night 更强调了时态是过去时，所以后半句应该用对过去情况的虚拟的从句，应该用相应的句式would have come

原句是 I think he must have been very busy last might, otherwise he would have come to the party.（我想他昨晚肯定很忙，要不然他会来参加聚会的。）
本句还可稍作变动，更好理解：
(I think)If he had not been busy last night, he would have come to the party.要不是他昨晚忙，他就会来参加聚会的。

Answer 4

因为去舞会是已经在昨天发生的事情。Would have come 是对过去时的虚拟。Would come只是将来时。