蹦极是一项极限体育运动，如图所示，A点最高点、B点为弹性绳自然伸长的位置，蹦极人在C点受弹性绳的弹力与自身重力相等，D点是能下落到的最低点．在蹦极人从A点下落到D点的过程中，　____ 　（填“B”、“C”或“D”）点动能最大，在这个过程中，减小的重力势能都转化为____ 能．（不计空气阻力）

    It's Sunday today. Sam and his friends are washing(洗)a car for Mr. Green. They can give the money from the car washing to their school football team. Mary and her friends are seeing a funny movie. They see an interesting cat in the movie. Ann is in the park with her mother. They're talking under a big tree. I think they are having a good time. Joan wants to know what her friend is doing. Her friend is in Japan, so Joan is writing a letter to her friend on her computer. May is cleaning the house with her parents. The family are very busy, but they're very happy. They are working and singing.