21、(3分)

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20、(1)_______________________________________________________________________

__________________________________________________________________(4分)

(2)_______________________________________________________________________

__________________________________________________________________(4分)

19、(5分)

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18、(4分)

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17、(4分)

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16、(4分)

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15、(9分)

(1)____________________，_____________________　　　　

(2)___________________________________________

(3)___________________________________________

14、(8分)

(1)_______________________________________________________________________

___________________________________________________________________(4分)

(2)_______________________________________________________________________

___________________________________________________________________(4分)