Icouldn'thavegottothemeetingontimeanearliertrain．A.ifIhadnotcaughtB.unlessIhadcaughtC.ifIdidnotcatchD.unlessIcaugh

Question

I couldn't have got to the meeting on time ________ an earlier train．
A. if I had not caught
B. unless I had caught
C. if I did not catch
D. unless I caugh

Answer 1

答案B
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：I 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.