某人造卫星运动的轨道可近似看作是以地心为中心的圆.由于阻力作用，人造卫星到地心的距离从r₁慢慢变到r₂，有E_k1、E_k2分别表示卫星在这两个轨道上的动能，则（    ）

A.r₁＜r₂，E_k1＜E_k2                          B.r₁＞r₂,E_k1＜E_k2

C.r₁＜r₂,E_k1＞E_k2                            D.r₁＞r₂,E_k1＞E_k2

A.R₁＜R₂，E_k1＜E_k2                                           B.R₁＞R₂，E_k1＜E_k2

C.R₁＜R₂，E_k1＞E_k2                                           D.R₁＞R₂，E_k1＞E_k2

A.r₁＜r₂,E_k1＜E_k2                             B.r₁＞r₂,E_k1＜E_k2

C.r₁＜r₂,E_k1＞E_k2                             D.r₁＞r₂,E_k1＞E_k2

（不定项选择）

A.r₁＜r₂,E _k1＜E _k2      B.r₁＞r₂,E _k1＜E _k2    C.r₁＜r₂,E _k1＞E _k2      D.r₁＞r₂,E _k1＞E _k2

A.r₁＜r₂,E_k1＜E_k2

B.r₁＞r₂,E_k1＜E_k2

C.r₁＜r₂,E_k1＞E_k2

D.r₁＞r₂,E_k1＞E_k2

某人造卫星运动的轨道可近似看作是以地心为中心的圆.由于阻力作用，人造卫星到地心的距离从R₁慢慢变到R₂，用E_k1、E_k2分别表示卫星在这两个轨道上的动能，则（　　）

A.R₁<R₂，E_k1<E_k2                                           B.R₁>R₂，E_k1<E_k2

C.R₁<R₂，E_k1>E_k2                                           D.R₁>R₂，E_k1>E_k2