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问题 选择题

关于导体的电阻，下列说法中正确的是（　　）

A．当加在导体两端的电压改变时，电压与电流的比值也随着改变

B．导体电阻与它两端的电压成正比，与通过它的电流成反比

C．粗细相同的导线，长的导线电阻较大

D．同种材料制成的长短一样的两条导线，细的电阻较大

答案

A、电阻的大小与施加在其两端的电压的大小无关，所以A是错误的；

B、欧姆定律只是反应了电阻在数值上与电压和电流的关系，但是电阻的大小与电流电压的大小无关，故B错误；

C、答案忽略掉了导体的材料，所以C是错误的；

D、综合考虑到了影响电阻大小的因素，且表述正确；

故选D．

判断题

人口过度增长不仅导致环境质量下降，还会破坏生态平衡。[ ]
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单项选择题

Right is right. Right7 Of course. But is left wrong Well, the Romans used to think so. They thought left-handed people were mistakes of nature. Latin, the language of the Romans, had many words that expressed this view. Some words we use today still have this meaning. The Latin word "dexter" means "right". The English word "dexterous" comes from this word. It means "handy" (clever with hands). So, right is handy. But the Latin word for left is "sinister". The English word "sinister" comes from this word. Sinister means "evil" (very bad). Is it fair to call right-handed people handy and left-handed people evil Well, fair or not, many languages have words that express such beliefs. In old English, the word for left means "weak". That isn’t much of an improvement over "evil".

Not very long ago, children were often forced to write with their right hands. Doctors have since found that this can be very harmful. You should use the hand you were born to use.

People who use their left hands are just starting to get better treatment. But why they get all these bad names in the first place One reason may be that there are not as many left-handed people as there are right-handed people. There is one left-handed person for every five right-handed ones. People who are different are often thought to be wrong. But attitudes do seem to be changing. Fair-minded right-handed people are finally starting to give left-handed people a hand.

The last sentence of this article means（）

A. fair-minded right-handed people want to change the habit of the left-handed people

B. fair-minded right-handed people are starting to help the left-handed people

C. fair-minded right-handed people are starting to use left hand to write and so on

D. fair-minded right-handed people are starting to give up using their left hands
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