he wasn't heard to sing in the classroom.为什么是to sing,不是singing或其他
问题描述：
he wasn't heard to sing in the classroom.为什么是to sing,不是singing或其他
答
因为这里并不强调他正在唱歌这个动作，有没有唱歌这样一个基本事实，所以不必用ing形式，hear someone do something的被动语态是加to 的不定式，所以只能用to sing
希望选为满意答案
答
这要看语态啊，要是正在进行 就用singing啊
答
nihao
be heard singing ------强调被听到的时候正在唱歌
be heard to sing ------强调唱歌的全过程都被听到了
答
这里是被动语态，被听见做某事是be heard to do sth
答
还原一下句子：We didn't hear him sing in the classroom.句子使用了 hear sb do sth 改为被动语态是：sb be heard to do sth,如果原句是：We didn't hear him singing in the classroom.改为被动语态就是：He wasn...
答
hear to do 表示动作的全过程 hear+ving 表示正在进行