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问题 选择题

某无色溶液中，能大量共存的一组离子是（　　）

A．Na+、Ag+、NO3-、MnO4-

B．Fe3+、H+、I-、HCO3-

C．K+、Na+、NO3-、ClO-

D．NH4+、Mg2+、SO42-、OH-

答案

A．该组离子之间不反应，但MnO4-为紫色，与无色不符，故A不选；

B．因Fe3+、I-发生氧化还原反应，Fe3+、HCO3-发生相互促进水解，H+、HCO3-结合生成水和气体，则不能共存，故B不选；

C．该组离子之间不反应，且均为无色，能大量共存，故C正确；

D．NH4+、Mg2+分别与OH-反应，则不能共存，故D错误；

故选C．

选择题

同等数量的黑白棋子，可以组成凌厉的攻势，也可以组成破绽百出的败局;人数和素质相同的劳动力，由于组织和安排不同，会引起生产结果的质的差异。这说明 ( )

A．事物的量变和质变是人的意愿可以左右的

B．量变和质变没有严格界限，只有大小、速度、程度、规模等方面的区别

C．量变引起质变,具有普遍性

D．事物总量不变，由于构成事物的成分在结构或排列次序上发生变化，也能引起质变
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阅读理解

Today there are policemen everywhere, but in 1700, London had no policemen at all. A few old

men used to protect the city streets at night and they were not paid.

In 1750, Henry Fielding started to pay a group of people to stop thieves. They were like

policemen and were called "Bow Street Runners" because they worked near Bow Street.

Fifty years later, there were 120 "Bow Street Runners", but London had become very big and

needed more policemen. So in 1829, London Police Force was started with 3,000 officers. Until

1920 all the police in London were men.

小题1:Who protected London in 1700?  (回答词数不超过4个)

小题2:When was London Police Force started?  ( 回答词数不超过2个)

小题3:Are all the London police men now?  (回答词数不超过1个)
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