题目

阅读下面短文，掌握其大意，然后从各题所给的四个选项（A、B、C和D）中，选出最佳选项。 Life is colorful. Sometimes it's just like potato salad;when it's shared, it became a picnic. With three young children to bring up, my husband John and Iwere very 1. Can we go on a picnic,Mom? my six-year-old daughter, Becky 2. Please. I had said no somany times in 3 months, and I decided the usual Saturdaymorning chores could 4. To her 5, I agreed. I prepared a few sandwiches and 6 a cooler with ice and drinks and called John 7. My eleven-year-old twin sons loaded the coo2013年12月15日4时35分，嫦娥三号着陆器与巡视器分离，“玉兔号”巡视器顺利驶抵月球表面．如图所示是嫦娥三号探测器携“玉兔号”奔月过程中某阶段运动示意图，关闭动力的嫦娥三号探测器在月球引力作用下向月球靠近，并将沿椭圆轨道在B处变轨进入圆轨道，已知探测器绕月做圆周运动轨道半径为r，周期为T，引力常量为G，下列说法中正确的是（　　）A．图中嫦娥三号探测器正减速飞向B处B．嫦娥三号在B处由椭圆轨道进入圆轨道必须点火减速C．根据题中条件可以算出月球质量和密度D．根据题中条件可以算出嫦娥三号受到月球引力的大小