题干
— are you going to become a famous pianist, Anna?
—I' m going to take piano lessons every day.
A：What
B：When
C：Where
D：How
答案(点此获取答案解析）
D
＝2 
， 
⊥ 
，当点P在y轴上运动时，点N的轨迹方程为( )