题干
．— Excuse me, could you tell me where I could make a call?
— Sorry, I’m a stranger here.
— ____.
A：Thanks a lot
B：That’s a pity
C：Thanks anyway
D：I’m sorry to hear that
答案(点此获取答案解析）
C
的焦点为圆心,且过坐标原点的圆的方程为 ( )