I see some boys( )(play)on the play ground all the time

问题描述:

I see some boys( )(play)on the play ground all the time

playing

see后面有两种形式
1、see sb.doing sth(看见某人正在做某事)
2、 see sb do sth(看见某人做某事)
你这个句子后面有all the time .就是经常发生的事,而不是正在进行的,肯定是用原形.
答案是:play