Now，people use satellites（卫星）to do many things．So far，man has invented four kinds of satellites．  1    of them is used to study the weather．Weather satellites can   2   any part of the world．They can watch clouds and strong winds moving across the earth and  3  many pictures of atmosphere（大气层） 4    the same time．The pictures    5    the weather stations by these satellites．Scientists can know   6   the weather will change by studying them，and then tell people in time．Weather plays an   7    part in people's everyday life．

Today，many weather stations in the world can receive satellite pictures．After receiving them，the scientists compare（比较）them with  8    ones．Perhaps they may find that the clouds    9    during the last few hours．This may mean that weather on the ground may  __10_  change soon．In their next forecast（预测），the scientists can   11  this．So satellite pictures are   12    to scientists．

__13   satellites were invented，the scientists could forecast the weather for about twenty-four or forty-eight   14  ．Now they can make good forecasts for three or five days．Thanks   15  weather satellites，people can know more about the weather．

1．A．Every one                             B．Each                                     C．One

2．A．reach                                  B．arrive                                 C．get

3．A．taking                               B．take                                   C．takes

4．A．of                                       B．in                                      C．at

5．A．were sent to                      B．are sent to                             C．send to

6．A．how                                    B．what                                  C．which

7．A．useful                               B．important                           C．useless

8．A．early                                   B．earlier                                 C．earliest

9．A．changed                              B．change                               C．have changed

10．A．also                                   B．too                                    C．either

11．A．talk                                   B．speak                                 C．say

12．A．helpful                               B．help                                   C．helping

13．A．After                                 B．Before                               C．When

14．A．weeks                               B．days                                  C．hours

15．A．to                                      B．for                                    C．at