情态动词的语法(4)

4) must表示对过去某时正发生的事情的推测，must 后面要接不定式的完成进行式。

---Why didn't you answer my phone call?

---Well, I must have been sleeping, so I didn't hear it.

5) 否定推测用can't。

If Tom didn't leave here until five o'clock, he can't be home yet. 如果汤姆五点才离开这儿，他此时一定还未到家。

21.6 表示推测的用法

can, could, may, might, must 皆可表示推测，其用法如下：

1）情态动词+动词原形。

表示对现在或将来的情况的推测，此时动词通常为系动词。

I don't know where she is, she may be in Wuhan.

2）情态动词+动词现在进行时。

表示对现在或将来正在进行的情况进行推测。

At this moment, our teacher must be correcting our exam papers.

这时，我们老师想必在批改试卷。

3）情态动词+动词完成时。

表示对过去情况的推测。

We would have finished this work by the end of next December.

明年十二月底前我们很可能已完成这项工作了。

The road is wet. It must have rained last night.

地是湿的，昨天晚上一定下雨了。

4）情态动词+动词的现在完成进行时。

表示对过去正在发生事情的推测。

Your mother must have been looking for you.

你妈妈一定一直在找你。

5）推测的否定形式，疑问形式用can't, couldn't表示。