or引导的虚拟语气

Question

He must have had an accident,or he __then.
A.would have been here
B.had to be here
为什么选a不选B？

Answer 1

He must have had an accident,or he __then.
A.would have been here B.had to be here
答案：A。
解释：全句子是含蓄条件句。前半句是情态动词must表示对过去事实的肯定推测，后半句表示与过去事实相反的假设，是虚拟语气。
翻译：他肯定发生事故了，否则，他本来已经到这里了。

Answer 2

这里虚拟并不是说有or的原因
因为情态动词的完成时表示虚拟
would是情态动词
类似的还有should have done 本应该
might have done本可能。。

Answer 3

选A。
He must have had an accident这句中，
must+ have done：对过去发生的行为肯定的推测。
然后or引导虚拟语气，后面也应该是对过去的事实进行虚拟。
表示过去的虚拟：If ... had done ..., ... would(might,could) have done..
因为情态动词后用动词原形，则为must have...
则用would have done形式。本回答被提问者和网友采纳