如图为染色体与DNA的关系图.下列有关叙述错误的是( )
A:①为主要遗传物质
B:③在人的体细胞中有23对
C:③的主要成分为①和②
D:①和②内均含有遗传物质
猜猜下面说的是哪种小动物。
Its ears are long. Its eyes are small. Its mouth is small. Its tail is short. What is it?
____
抛物线y=x2﹣4x+c与x轴交于A、B两点,已知点A的坐标为(1,0),则线段AB的长度为____ .
________ you have a good time yesterday?