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问题 单项选择题

根据建筑安装工程定额编制的原则，按平均先进水平编制的是( )。

A．预算定额

B．企业定额

C．概算定额

D．概算指标

答案

参考答案：B

解析：制定企业定额应以企业平均先进水平为基准，使多数单位和员工经过努力，能够达到或超过企业平均先进水平，以保持定额的先进性和可行性。

判断题

证券自营业务是指经中国证监会批准经营证券自营业务的证券公司用自有资金和依法筹集的资金，用自己名义开设的证券账户买卖有价证券，以获取盈利的行为。( )
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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.

The purpose of the scientists in studying tree ring is to ().

A. examine the chemical elements in Ice Age

B. look into the pattern of solar wind activity

C. analyze the composition of different trees

D. find out the origin of carbon-14 on earth
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