A:x+12=6;
B:x+22=6;
C:x-12=8;
D:x-22=8.
将圆 {x=2cosθ,y=2sinθ ( θ 为参数)上的每一个点的横坐标保持不变,纵坐标变为原来的 12 ,得到曲线 C .
--- How long may I your bike?
--- For a week. But you mustn't it to others.