题目

Puppy FoodA puppy (young dog) is a precious addition to any family. The excitement of bringing home a little furry friend will always live in our memories. Like all of us, though, your puppy must have adequate nutrition right from the start to make certain that it'll have a long and healthy life.【1】 You might ask yourself what is the best for your new pet with all of the different varieties on the market in all of their attractive packaging. Some dry food produced specially for puppies is the best for the development of their teeth. 【2】Contrary to the belief of many first-time puppy ow4．某人造地球卫星因受高空稀薄气体的阻力作用，绕地球运转的轨道会慢慢改变．每次测量中卫星的运动可以近似看作圆周运动．某次测量卫星的轨道半径为r1，后来变为r2，r2＜r1．以Ek1、Ek2表示卫星在这两个轨道上的动能，T1、T2表示卫星在这两个轨上绕地球运动的周期，E1、E2表示卫星在这两个轨上的机械能．则（　　）A．Ek2＜Ek1，T2＜T1，E1=E2B．Ek2＜Ek1，T2＞T1，E1＞E2C．Ek2＞Ek1，T2＜T1，E1＞E2D．Ek2＞Ek1，T2＞T1，E1＜E2