good for our health.A. Do exercise isB. Doing exercise is C. Do exercises areD. Doing exe

问题补充：

good for our health.

A. Do exercise is

B. Doing exercise is

C. Do exercises are

D. Doing exercises are

答案：

A. Do exercise is

(答案→)B. Doing exercise is

C. Do exercises are

D. Doing exercises are

解析：句意：做锻炼有利于我们的健康。do exercise做锻炼，exercise当锻炼时，是不可数名词，没有复数形式。be good for对……有好处；利于。此处作主语，故用动名词短语，动名词短语做主语，谓语用单数形式。故选B。