B

    Kate is an English girl. She lives in a tall building in the city of London. There are sixteen floors in the building, and she lives on the tenth floor. She uses a lift(电梯) to go up and down.

    Kate studies in a middle school near her house and she works hard. She goes to school early. Every day she leaves her home at half past six. She walks to the lift, and it takes her down to the first floor.

    There is a bus stop near the building. Usually she takes the No. 7 bus to her school. Classes begin at eight. She goes to play games at three forty. She gets home at a quarter past five. She begins to do her homework at eight and finishes it at half past nine.

坚持绿色发展，建设生态文明，关系人民福祉。保障生态环境，共建美丽家园，公民责无旁贷。

卫星通信系统由卫星和地面站两部分组成。卫星在空中起中继站的作用，即把地面站发上来的电磁波放大后再返送回另一地面站。地面站则是卫星系统与地面公众网的接口，地面用户通过地面站出入卫星系统形成链路。由于同步卫星在赤道上空约36 000 km处，它绕地球一周的时间恰好与地球自转一周时间（23 h 56 min 4 s）一致，从地面看上去如同静止不动。3颗卫星就能覆盖整个赤道圆周。故卫星通信易于实现越洋和洲际通信，最适合卫星通信的频率是1～10 GHz频段，即微波频段。