Question

http://v.ku6.com/show/QWCphRtZKpMwAuPO.html 这个视频短片的英文和翻译.谢了.

Answer 1

When a bird flies,its wings make two kinds of movements:当一只鸟飞翔时,它的翅膀在做两种运动：The inner part of the wings moves up and down,the outer part moves in a circle.翅膀的根部上下运动,尾部圆形...