题目

How many people have I met who have told me about the book they have been planning to write but have never found the time? Far too many. This is life, all right, but we do treat it like a rehearsal(排演)and, unhappily, we do miss so many of its best moments. We take jobs to stay alive and provide homes for our families always making ourselves believe that this style of life is merely a temporary state of affairs along the road to what we really want to do. Then, at 60 or 65, we are suddenly presented with a clock and several grandchildren and we look back and realize that all those years wai地球绕太阳的运动可视为匀速_周运动．由于太阳内部的核反应导致太阳的质量不断减小，而使万有引力变小．若干年后，地球绕太阳的运动情况与现在相比（　　）A．运动半径变大B．运动周期变大C．运动速率变大D．运动角速度变大