the missing children were last seen__(play) by the river.

题目

the missing children were last seen__(play) by the river.
答案是playing why?感官动词变被动不是要还原to吗

答案

从语法上讲,填 playing 和 to play 都对.
sb be seen doing sth 被看见正在做某事
sb be seen to do sth 被看见做某事
从意思上来看,填 playing 更好,句子意思是：
那个失踪的男孩最后一次被看见时正在河边玩耍.