I coutdnt have got to the meeting on time an earlier train.A. if I had not caughtB. unles

问题补充：

I coutdn 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：

A. if I had not caught

(答案→)B. unless I had caugh

C. if ! did not catch

D. unless I caugh

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。