问题
选择题
Only ________ according to the directions can the medicine be quite effective.
A．taking
B．taken
C．being taken
D．having been taken
答案
答案：B
选项动词的逻辑主语the medicine与动词take之间为被动关系，实际上相当于一个时间状语从句only when it is taken...结构，故应选taken在句中用作状语。
