题目内容：

I don't know whether to take the medicine at once.If I ______ ,I ______ it
A.knew,would take
B.had known,would have taken it
C.knew,would have taken
D.had known,would take

优质解答

不管采不采纳,我的回答就在这里

这题选B

考点是虚拟,因为A是对现在的虚拟,主句would +动词原型,从句用过去式
b 是对过去的虚拟,主句用would +现在完成时,从句用过去完成时

CD 语法就错了,时态用的不对

这里,根据上下文,我不知道,我是否现在得吃药,要是我早知道的话,我早就吃了.

重点是,后面,表达的是,我以前要是知道的话,他就会吃