Generally speaking, according to the directions, the drug has no side effect.
A. when taking
B. when taken
C. when to take
D. when to be taken
网友回答
A. when taking
(答案→)B. when taken
C. when to take
D. when to be taken
解析：句意：一般地说，当按照说明书来服药的话，药就没有副作用。这里空格处是省略句，完整的是when it is taken according to the directions；整个句子的主语是drug，当从句的主语与主句的主语一致，并且从句的谓语动词有be时，这时可以把主语和be都省去，这里drug与take之间是被动关系，故用被动语态，这里可以用it代替the drug，把it is省去了，故选B。