After a bird has flown from one tree to another, what trace does it leave in the air?
After a bird has flown from one tree to another, what trace does it leave in the air?
当一只鸟从一棵树飞到另外一棵树时，牠在空中留下什麽痕迹呢？
After a bird has flown from one tree to another, what trace does it leave in the air?
当一只鸟从一棵树飞到另外一棵树时，牠在空中留下什麽痕迹呢？