问
Our friends' plane landed but they weren't on it. They ____ the plane. A. can have missed B. may have missed C. can have lost D. may have lost 我知道答案是 B。但是我不明白为什么不可以选 A。can have done 不是也可以表示推测吗？
答
can have done 虽可对过去事件的可能性表示推测,但是它只能用在否定句和疑问句中。因此,它不能用在上面的肯定句中,见 can 。