In our school, we have four classes in the morning. From nine forty to ten o'clock, we can have a twenty-minute rest time. It is a quarter to ten now. Look! Most of us are going out of the classroom. Some boys are playing basketball, soccer or running on the playground. Some girls are watching them or playing badminton. There are also some students in the classroom. They are talking. A few of them are reading or doing homework. Look! A girl is looking at the birds in a tree from the window. She is smiling.

    What are our teachers doing? They are either working or talking to the students in the office. They are all very busy but happy!

世界陆地的最低点是

2011年4月10月，我国在西昌卫星发射中心用“长征三号甲”运载火箭，成功将北斗八号导航卫星发射到预定椭圆轨道，该椭圆软道近地点约200千米，远地点约3599千米，如图是北斗八号一导航卫星的轨道示意图。已知该卫星沿椭圆轨道绕地球运行的过程中机械能守恒，则关于该卫星从远地点向近地点运行过程中势能、动能、速度的变化是（）

下列关于亚洲人口的叙述，正确的是（      ）