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问题 单项选择题

水银温度计中封闭着一定量的水银，在用这种温度计测量温度的过程中，水银发生热胀冷缩，下列说法正确的是：（）

A.温度计中水银的质量不变

B.温度计中水银的体积不变

C.温度计中水银的高度不变

D.温度计中水银的温度不变

答案

参考答案：A

单项选择题

在国际许可合同中，如果规定在合同规定的范围和期限内，只允许被许可人使用该技术，许可人不得在该地域内使用该技术，也不得将此项技术向第三者转让，这种许可合同属于什么合同( )

A．独占许可合同

B．排他许可合同

C．交叉许可合同

D．从属许可合同
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单项选择题

You can tell the age of a tree by counting its ring. But these records of a tree’s life really say a lot more. Scientists are using tree ring to learn what’s been happening on the sun’s surface for the last ten thousand years. Each ring represents a year of growth. As the tree grows, it adds a layer to its trunk, taking up chemical elements from the air. By looking at elements in the rings from a certain years, scientists can tell what elements were in the air that year. Dr. Stevenson is analyzing one element, carbon-14, in ring from both living and dead tree. Some ring go back almost ten thousand year to the end of the Ice Age. When Stevenson followed the carbon-14 levels changed with the intensity of solar burning. You see, the sun has cycles. Sometimes it bums fiercely, and at other times it is relatively calm. During the sun’s violent periods, it throw off charged particles in fast moving streams called "solar winds". The particularly interfere with the formation of carbon-14 on earth. When there is more solar wind activity, less carbon-14 is produced. Ten thousand years of tree ring show that the carbon-14 level rises and falls about every 420 years. The scientists concluded that solar wind activity must follow the same cycle.

When the sun burn fiercely, () carbon-14 is produced.

A. less

B. more

C. no

D. much
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