Genarally speaking,__according to the directions ,the drug has no side effect.

题目

Genarally speaking,__according to the directions ,the drug has no side effect.
A.when taking B.when taten C.when to take D.when to be taken
选哪个呢,

答案

B
省略了When the drug is taken according.
这种句子要看后面的主语了,如果说后面的主语是动作的执行者,则前面用现在分词来表示主动关系.
例：
Knowing a lot from his teacher,he went on his research.
从他老师那知道很多之后,他继续他的研究.（由于是he自己know a lot的,所以用ing表示主动关系.）
如果后面的主语是动作的承受着,哪么用过去分词表被动关系.
像你题目中的这句就是.
再例：
Seen from the mountain,the city is small.
从山顶上看,这个城市很小.
由于城市是被看的,所以用seen.
OK?