generally speaking,_____according to the directions,the drug has no side effect.

Generally speaking,_____according to the directions,the drug has no side effect.
a.when taking.b.when taken. c.when to taked.when to be taken
答：B
译：一般说来,如果按说明书服用的话,这药是没有副作用的.
析：when taken...= when it is taken ...=when the drug is taken .
本题考查状语从句的省略,当状语从句中的主语与主句主语相同(或为it) ,且谓语中有be动词时,可以省略"主+be".
也可以认为是考查非谓语动词,作状语时,为明确是什么状语,可在分词前加上连词when, before等等.
作状语用的分词的选择取决于其逻辑主语（即主句的主语）与它的关系.这里the drug与take (服用）是被动关系,不能选用现在分词主动一般式taking,排除A.
不定式作目得状语,when+不定式为疑问不定式,一般作宾语（主语）,不作状语,排除CD