题目

补全对话 A. Let's play! B. It sounds boring. C. Is this your volleyball? D. Do you have a soccer ball? E. Where is your soccer ball? F. Do you have a tennis ball? G. Where is my ping-pong ball? A: Hello, Jack! We can play tennis.B: Oh, no, I don't. I only have a tennis racket (球拍).A: B: No, it isn't. It is my brother's. And I can't play volleyball.A: B: Yes, I do. I'm good at it.A: B: Um...Oh, it is under the bed.A: Good! B: OK, let's go.已知椭圆的左、右焦点分别为F1（-1，0）、F2（1，0）点在这个椭圆上．（1）求该椭圆的标准方程；（2）过点F1的直线l与该椭圆交于M、N两点，求线段MN的中点P的轨迹方程．