阅读下列短文, 掌握其大意, 然后从1￣20各题所给的四个选项中, 选出一　　 个最佳答案。

    All sounds are different. Some may be 1　　 , others may be loud. Some sounds are high, others are 2.

    Some sounds are useful. Without sound we cannot 3 or listen 4 one　　 another. The ringing alarm clock wakes 5. The hooting of a horn on the　　 road warns careless people 6.

    Some sounds are harmful. Very loud sounds 7 huge planes which fly　　 low over the land can cause damage to houses. Loud sounds will disturb　　 people. Very loud sounds can even make people 8 or prevent them 9　　 hearing clearly.

    Collect 10 solids as you can find, for example, coins, rocks, tins,　　 pieces of wood and glass. Take two 11 objects and knock them　　 together. Then take different objects and knock them together. Try to　　 make as many different sounds as possible.

    Next take two objects and rub them together. Then take different　　 objects and rub them together. Try to make many different sounds.

    Whenever you hear a sound, find out 12 it comes from and what　　 causes it. We make sounds 13 things move to-and-fro. This to-and-fro　　 14 is called vibration. It means moving up and down or forwards and　　 backwards very fast. These vibrations cause the air 15. This makes　　 sound waves. Look at this picture. Hold a long ruler on the table so　　 that 16 of the ruler is jutting 17 the table. 18 down on the free end　　 of the ruler and let go. See the ruler 19. Can you 20 a humming sound?

(1) A. soft    B. gentle    C. light    D. thin

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(2) A. long    B. thick    C. low     D. heavy

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(3) A. do    B. make    C. talk    D. produce

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(4) A. at with    B. from    C. by    D. to

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(5) A. a persons    B. people up    C. people get up    D. persons get up

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(6) A. dangerous    B. in dangerous    C. danger    D. of danger

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(7) A. produce    B. produced    C. produce by    D. produced by  

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(8) A. deaf    B. deafen    C. to deafen    D. deafening

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(9) A. out     B. from    C. in    D. on

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(10)A. so many    B. as many    C. such more    D. so more

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(11)A. similar    B. like    C. same    D. the same

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(12)A. in which    B. which    C. where    D. a place

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(13)A. in doing    B. by doing    C. in making    D. by making

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(14)A. motion    B. move    C. movement    D. moving

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(15)A. vibration    B. to vibrate    C. vibrate    D. vibrated

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(16)A. two-third　　    B. second-three    

C. seconds-third    D. two-thirds   

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(17)A. on    B. out    C. out of    D. off

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(18)A. Pull    B. Push    C. Hold    D. Take

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(19)A. vibrating    B. to vibrate    C. vibrate    D. vibrated

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(20)A. know    B. recognize    C. record    D. hear

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