I often hear John (sing/singing/to sing)in his room.为什么这里要填sing
问题描述：
I often hear John (sing/singing/to sing)in his room.为什么这里要填sing
答
sing
前面有个often指经常发生的动作,所以不用现在分词,singing是表示听见他正在唱歌,而且hear sb 后面是不能加to的,所以选sing