--- What should I do, doctor?
--- healthy, you should take more exercise.
A. Keep
B. To keep
C. Keeping
D. To keep out
网友回答
A. Keep
(答案→)B. To keep
C. Keeping
D. To keep out
解析：考查非谓语动词.句意:医生,我该做什么?_为了保持健康,你应该多锻炼.不定式作目的状语,表示具体的将要进行的动作, keep out是阻止进入的意思,keep是保持的意思,故选B.