We often hear a lot of birds ___(sing) in the trees in the morning.寻英语达人解答.
问题描述：
We often hear a lot of birds ___(sing) in the trees in the morning.寻英语达人解答.
答
we often hearalot of birds (singing) in the treesin the morning.
hear sb/sth doing sth
答
sing
hear sb do sth.听见某人做了某事。
答
填sing