Question

高一英语 ...情态动词和虚拟语气

1 ---Why didn't you put your cellphone in your overcoat pocket?
---I ______, but I was afraid it would be stolen.
A had put B would have 能说明理由吗

2 ---Why aren't they here yet?
---They _______ the bus
A can have missed B may have missed C might be late for (A和B有什么区别? might只能用于过去时吗?)

3 could have done 和 can have done有什么区别？

Answer 1

1. B
这是would have put的省略，情态动词+have done表示对过去的推测。如should have done本应该做某事，can/couldn't have done不可能做了某事，may/might have done可能做了某事，等等。
I would have put it in my overcoat pocket我本来把它放在我的上衣口袋里

2.B
从题意来看，这里是表示推测。can表示推测时只用于否定句或疑问句中。can have done意思是“本来能做却未做”，不是推测。
might也可用于现在时，这时它的肯定性比may更小。说话者对一件事更不确信时就用might。

3.can have done意思是“本来能做却未做”，不是推测。
could have done一是can have done的过去时，一是can have done的委婉说法。

Answer 2

1. B would have是would have done的省略形式，是虚拟语气。
2. B 表示对过去的情况的猜测，may have done表示（过去）可能做了某事
can have done 不用于肯定句
3. could have done 有两个意思：一是虚拟，“本可能做某事”；二是猜测“过去可能做了某事”
can have have不能表示虚拟，通常用在疑问句和否定句中，表猜测