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问题 选择题

如图所示，一个原来不带电的金属球壳内，在其球心放一个负点电荷，那么关于A、B、C三点的电势、、的关系正确的是（        ）

A、          B、

C、          D、

答案

答案：A

题目分析：因为金属球内放置的是一个负电荷，故电场线指向负电荷，沿电场线方向电势降低，所以A的电势大于导体的电势，导体的电势又大于c点的电势，A是正确的。

填空题

盐能与许多物质发生复分解反应，请分析下列化学反应，回答问题：

①BaCl2+H2SO4==BaSO4↓+2HCl ②CuSO4+2NaOH==Cu(OH)2↓+Na2SO4

⑴从反应物的类别分析，①是盐与酸的反应，②是盐与________的反应

⑵从复分解反应发生的条件分析，①和②都能反应的原因是生成物中都有__________；

⑶利用K2CO3溶液和_________溶液反应，可制取KOH。
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单项选择题

If you often feel tired and the doctor can’t find anything wrong with you, you may be in a state of Subhealth (亚健康). Subhealth is a state between health and illness. Most of the subhealthy people are middle-aged ones who are usually stressed out because of work and family. And some of them are students who are having exams.
If you are subheahlty, it is not difficult for you to become well soon. You should have good living habits. For example, you should get up early and go to bed early. And you should exercise regularly. Exercising can keep you healthy. As for meals, it is better to eat less salt and sugar. Vegetables, fruit and fish are important to your body. You should eat more of them. It is not good to eat too much at one meal, because it may cause unhealthy changes in the digestive tract(消化道). And at last, a balanced diet is very helpful in staying away from subhealth.

How may you feel if you’re subhealthy

A. Happy
B. Comfortable
C. Tired
D. Sad
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