Many scientists say that the world is getting hotter and hotter．If they are right , the ice at the North and South Pole will melt eventually．If this happens, the sea will  1  and may cover most  2  all of Singapore．This will force everybody to move to a  3  country．

       We know that the sun  4  the earth．The heat from the sun hits the  5  , and some of 6  goes back into the sky．However, factories and cars  7  a lot of carbon dioxide（二氧化碳）．When the gas rises into the sky, the heat from the sun can come  8  them but the heat from the ground cannot．It  9  near us in the sky and makes the  10  hotter and hotter every year．

Scientists call this the “greenhouse effect” because a greenhouse is a small glass  11  which is hot inside．It is used for  12  plants in cool countries．Many countries are  13  about the greenhouse effect．They are trying to stop factories and cars from sending  14  gases into the sky．Scientists are not sure when the world will get much hotter．Some people say that the greenhouse effect has  15  already and has begun to affect the world’s weather．

1．A．rise                          B．fall                         C．change                   D．disappear

2．A．and                          B．or                           C．but                         D．till

3．A．better                       B．larger                      C．safer                      D．farther

4．A．shines                   B．circles                    C．covers                    D．heats

5．A．ground                     B．sky                         C．mountain                D．forest

6．A．them                        B．it                            C．those                      D．such

7．A．make                        B．spread                    C．produce                  D．from

8．A．through                    B．over                       C．into                        D．toward

8．A．hides                        B．continues                C．follows                   D．stays

10．A．cloud                      B．air                          C．season                    D．temperature

11．A．building                   B．flat                         C．tool                        D．machine

12．A．putting                    B．storing                    C．cutting                    D．growing

13．A．excited                   B．disappointed            C．worried                  D．pleased

14．A．dangerous               B．harmful                   C．heavy                     D．useful

15．A．meant                     B．improved                C．started                    D．stopped