What should I do doctor?- healthy you should take more exercise.A. KeepB. To keep

问题补充：

--- What should I do, doctor?

--- healthy, you should take more exercise.

A. Keep

B. To keep

C. Keeping

D. To keep out

答案：

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.