Generally speaking according to the directions the drug has no side effect.A. when takingB

问题补充：

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

答案：

A. when taking

(答案→)B. when taken

C. when to take

D. when to be taken

解析：此题考查非谓语动词作状语的用法。动词不定式一般不作时间状语，故先排除C、D两项。分词作状语，表示主动关系时用现在分词，表示被动关系时用过去分词。根据句意，应用B项，when taken=when the drug is taken。全句意思是：一般来说，药品在根据说明书服用时是没有副作用的。