The missing boys were last seen___ near the river.a,playing b,to be playing c,play d,to play

问题描述:

The missing boys were last seen___ near the river.a,playing b,to be playing c,play d,to play
选哪个,为什么?

a
句子的意思是最后一次看见失踪的男孩们是他们在河边玩耍.
考的结构是see sb.do/doing sth.排除b和d
男孩们是被别人看见在玩耍所以用被动语态
强调他们被别人看见的时候正在玩耍所以用playing