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问题 选择题

浓硝酸和锌的反应的化学方程式为：Zn+4HNO3=Zn（NO3）2+2H2O+2X↑，则X为（　　）

A．H2

B．NH3

C．NO

D．NO2

答案

根据质量守恒定律和Zn+4HNO3=Zn（NO3）2+2H2O+2X↑可知，每个X中含有1个氮原子和2个氧原子，是二氧化氮，二氧化氮的化学式是NO2．

故选：D．

选择题

Why don’t you ______ your friends to the party ? We have enough food.

A．bring

B．brings

C．leaves

D．take
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选择题

—Where is your new home now?

—In the new developed zone. But I ______downtown for five years.[ ]

A. have lived    

B. had lived  

C. 1ived

D. was living
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