I think ____(do) exercise is good for health

问题描述:

I think ____(do) exercise is good for health
do 是加ing还是原型,若加ing 这件事情得是主语,而现在I是主语,那么do是什么形式,

doing
因为think 后面省掉了(that),所以是从句,后面是个完整的句子,所以+ing