题目

题型：不详难度：来源：

I coutdn"t have got to the meeting on time____________ an earlier train.

A．if I had not caught	B．unless I had caugh
C．if ! did not catch	D．unless I caugh

答案

B

解析

if．．．not和unless有时也不能互相替换。unless不能用于“由于未发生B而发生A”的句子里，如：1 will be quite斟ad if she does not come this evening。unless常用来引导一个谈及过去的事后的想法，unless从句跟着主句，通常用破折号而不是逗号将它与主句分开。