Follow the directions on the bottle carefully when .
A. you will take the medicine
B. taking the medicine
C. to take the medicine
D. taken the medicine
网友回答
A. you will take the medicine
(答案→)B. taking the medicine
C. to take the medicine
D. taken the medicine
解析：主句中没有主语是祈使句，用现在分词表示时间语主语(you)一致。