鸟类的体型有利于它飞行时减少飞行阻力,它的体型是( )
A:流线型
B:扇形
C:长方体形
D:侧扁形
头发乌黑通直、脸庞扁平的是 ( )
根据短文,判断正误。
Look at this desk. It's Jim's desk. It's brown. Jim's book is on it. It's an English book. His pencil-box is on it, too. His pencil is in his pencil-box. But where's his pen? He can't find it.
芦苇的茎不能无限制的加粗,原因是它的维管束内没有( )
中国是世界上金鱼品种最多的国家.形成众多金鱼品种的原因是( )