I often hear birds ( )in the morning?是填to sing 还是填singi

题目

I often hear birds ( )in the morning?是填to sing 还是填singi

答案

我觉得都不对,应该是sing
hear sb do或doing,而singing表示正在唱歌,often暗示是经常发生的事,应该用表示一般现在状态的sing