During the winter holiday, Ted learned ____ (skate) on the real ice.
用动物细胞工程技术获取单克隆抗体,下列实验步骤中错误的是
Every ton of this recycled paper uses 90 liters of water in its ________.
如图,AD、BC是⊙O的两条互相垂直的直径,点P从点O出发,沿O→C→D→O的路线匀速运动.设∠APB=y(单位:度),那么y与点P运动的时间x(单位:秒)的关系图是( )