Question

英语真正的语法高手进吧

The missing boys were last seen ____ near the river.
A. playing B. to be playing C. play D. to play
我们知道宾补在变为主补时要还原to，
那么本题主动的see变为 were last seen后是否在其后加上to？
到底选择哪个答案假如是A答案的话to到哪里去了呢？
请具体结合例子讲解 谢谢
有这样的例子 I saw her cross the road变为被动后是She was seen to cross the street.

Answer 1

选B. to be playing
SEE的被动态句型为:
be seen to do sth. / be seen to be doing sth. "被看到做某事/正在做某事"

Answer 2

答案选A，see后面既可以接不定式作宾补，也可接现在分词做宾补，要根据句义来定，此句明显是说，：这个孩子最后次被见到的时候正在河边玩，也就是说看见与玩两个动作同时发生，所以只能用现在分词。