To make us healthier, the teachers often see us on the playground.
A. took exercise
B. take exercise
C. take exercising
D. to take exercise
网友回答
A. took exercise
(答案→)B. take exercise
C. take exercising
D. to take exercise
解析：句意：为了让我们更健康，老师们常常看着我们在操场上锻炼。See后面接不带to的不定式做宾语补足语，表示看见某人做某事。Exercise本身即可表示锻炼这一抽象动作，故选B。