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    There are many reasons for it. When the sun __2__, it is day. When the sun sets, it is night. Days are warmer than nights. This is __3__ the sunshine falls on the earth during the day. The sunshine makes the land, the water and the air warm. At night when the sun is not there, it is __4__. In the mornings and in the evenings the sunshine is slanting(斜射). So it is not very hot. At noon the sunshine falls __5__ on the earth, and it is very hot.

    We know that the earth goes __6__ the sun. When one half of the earth is close to (就近) the sun, the other half is __7__ from it. The part of the earth closer to the sun is summer. Here the days are warmer and longer. And the part of the earth away from the sun is winter. Here the days are cooler and __8__. For example, when it’s winter in China, it is summer in Australia.

    People can __9__ the weather, too. We know the temperature on the earth is getting warmer and warmer. This is because the environment has been polluted and destroyed . Now the weather is much worse than before. It’s very terrible. If we want to __10__ our environment, something useful should be done immediately.

(    )1. A. must　　   B. can’t　　       C. may　　        D. should

(    )2. A. rose　　    B. rises　　        C. rising　　       D. sets

(    )3. A. why　　  B. because　　    C. how　　        D. when

(    )4. A. cooler      B. coolest　　      C. hot　　　　     D. hottest

(    )5. A. straight     B. straightly        C. slant　　       D. slanting

(    )6. A. over　　  B. in　　　　      C. round　　      D. below

(    )7. A. off　　   B. wide　　       C. high　　        D. away

(    )8. A. long　　    B. short　　       C. shorter　　     D. longer

(    )9. A. get　　     B. be　　　　     C. become　　    D. change

(    )10. A. improve  B. improves        C. improved        D. improving