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问题 选择题

下列说法不正确的是(    )

A．金属钠很软，可以用小刀切割

B．自然界中的钠只能以化合态存在

C．因为钠可以保存在煤油中，所以钠着火时可以用煤油灭火

D．钠离子半径比钠原子小

答案

答案：C

C项中煤油本身是易燃物，因此不能用煤油灭火。而D项中Na+比Na原子少一个电子层，故半径比Na原子小。

改错题
短文改错

      In my village a lot of children were leaving school for various
reason.Some families are too poor to send their children to school,and they
have to earn money to support their families.Many parents do not think it useless
to send their children to school.They would rather let their children to stay at home.
I feel worried this.I think every child should have
a chance to go to school.We should pay
many attention to the education of children,
for we will play an important part in our socialist construction in the future.Ways must
be found prevent children from leave off their studies.


1. _____
2. _____
3. _____
4. _____
5. _____
6. _____
7. _____
8. _____

9. _____
10. _____
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单项选择题

公园给水管网布置，在不冻或轻冻地区，覆土深度应不小于（）cm。

A、40；

B、50；

C、60；

D、70。
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