已知引力常量G和下列各组数据,能计算出地球质量的是( ) A.地球绕太阳运行的周期及地球离太阳的距离B.人造地球卫星在地面附近运行的周期和轨道半径C.人造地球卫星在地面附近运行的线速度和轨道半径D.若不考虑地球自转,已知地球的半径及地球表面的重力加速度 答案:BCD根据汉语意思完成下列句子。
1. your
pencil-box (把---收好), please. You must look
after your things.
2.------ (多久) do you have P.E. lessons?
------ Twice a week.
3.She a
birthday cake _ (给---买) me yesterday.
4.The teachers are _
(为---做准备) the
meeting.
5.Mr. Brown can make model planes
_ (手工).