题目内容：

The experiment shows that proper amounts of exercise,if ______ regularly,can improve our health
A.being carried out
B.carrying out
C.carried out
D.to carry out
为啥不是A?

优质解答

这里是省略了相同的主句及be动词,整句完整的话应该是：The experiment shows that proper amounts of exercise,if the proper amouts of exercise is carried out regularly,can improve our health.或者the proper ...