This medcine,if___ according to the directions,has no side effect.

问题描述:

This medcine,if___ according to the directions,has no side effect.
A.take B. to take
C. taking D.taken
选啥 原因是什么.. 选B为啥不行?
答案上是D

是D啊.首先确定一下这个句子的语态,药肯定是被人吃的,所以整个句子是一个被动语态的结构.被动语态应该是be动词加动词的过去分词结构,这个句子中实际上是省略了be动词.如果把if提到句首,就应该变成If this medcine (is taken )according to the directions,has no side effect.