can could 的区别与用法表示请求造句

　　When can I get my test results?

　　我什么时候可以拿到化验结果？

　　We can reduce the problem to two main issues.

　　我们可以将这个问题概括成两个要点。

　　How long can a human being go without sleep?

　　人不睡觉能活多久？

　　The operation could prolong his life by two or three years.

　　这次手术可使他多活两三年。

　　I could come next week, or the week after.

　　我可能下周来，或者再下一周。

　　You could see from his face that he was lying.

　　从他的表情上你可以看出他在说假话。