已知圆x²+y²=4上任意一点P在x轴上的射影为H，点F满足条件$\overrightarrow{OH}$+$\overrightarrow{OP}$=2$\overrightarrow{OF}$，O为坐标原点．

求点F的轨迹C的方程；

读我国沿36°N的地形剖面图，图中一、二、三阶梯对应的地形区分别是(     )

阅读理解

B

    "I'm trying to do extra chores so I can make enough money to buy the new Space Invaders video game, but there's nothing to do," Michael sighed.

    "You could offer to wash Mom and Dad's cars," Greg said. “Some neighbors would pay you to wash theirs, too." Michael nodded. The air was cold. He shivered(颤抖) at the thought of washing cars and getting wet in this cold weather. "Maybe this isn't a good idea."

    "I have some golf gloves that are designed for wet and cold weather. You can wear them, and I'll even help you wash the cars," Greg said.

    "Really? You would help me and let me keep the money?"

    "Sure. Golf season is over. I won't need the extra cash for a while."  Greg disappeared inside the house. And soon, Greg came back with the gloves.

    Michael asked his parents if he could wash their cars for a small fee. When they agreed, he asked some neighbors, too. Three more agreed. After washing the cars, Michael got enough money for that video game.

    Greg drove Michael to the mall. Michael found the game immediately, but as he took it off the shelf, he saw a golf video game next to it. Michael looked at Greg and thought of how he had helped him. Greg loved golf and wouldn’t play golf again until spring, unless… Michael put his game back and brought the golf game to the register.