講義
can not have + p.p. 指現(xiàn)在對過去的動作認為不可能
She can not have gone to the movies with Danny at eight last night.
她昨晚八點的時候不可能跟Danny去看電影。(那個時候她跟我在家一起看電視。We were watching TV at home at that time.)
You can't have seen him this morning. He left for America yesterday.
你今天早上不可能看到他,他昨天就去美國了。
could 可表示禮貌的請求或建議,并非指過去
Could you please give me your phone number?
可以給我你的電話號碼嗎?
Could you wait for me ten more minutes? 你可以再等我十分鐘嗎?
Could I stay here a little longer? 我可以在這兒多待一會兒嗎?