英语单选题如下:-----What did he do in the middle of the night?-----
2个回答

hear sb do sth = sb be heard to do sth (变成被动语态时不定式要还原)

另外,hear sb doing sth = sb be heard doing sth (指动作正在进行)不可能是 to be playing ...

根据句意‘经常被听到弹钢琴’ 不是正在进行的动作,故是 to play the piano