you have heard the song ,you will never forget it

问题描述:

you have heard the song ,you will never forget it
(              ) you  have  heard  the  song   ,you  will  never  forget  itA .  if  B.  unless  C.once  D.though 选哪一个,说一下理由...

C.once
译:一旦你听过这首歌,你将永远不会忘记.
B/D的错误应该显而易见,语意不对;
主要要甄别的是A .if.if不合适,是因为若if引导的从句表条件的话,you have heard the song 的时态不对,应该是you hear the song;否则就应该改成虚拟语气了