若实数a<b,则化简(a-b)2的结果为( ) A.a+b B.a-b C.-a-bD

题型:选择题

问题:

若实数a<b,则化简
(a-b)2
的结果为(  )
A.a+bB.a-bC.-a-bD.-a+b
考点:二次根式的定义
题型:选择题

When Dr. John W. Gofman, professor of medical physics at the University of California and a leading nuclear critic, speaks of "ecocide" in his adversary view of nuclear technology, he means the following. A large nuclear plant like that in Kalkar, the Netherlands, would produce about 200 pounds of plutonium each year. One pound, released into the atmosphere, could cause 9 billion cases of lung cancer. This waste product must be stored for 500,000 years before it is of no further danger to man. In the anticipated reactor economy, it is estimated that there will be 10,000 tons of this material in Western Europe, of which one table-spoonful of plutonium-239 represents the official maximum permissible body burden for 200,000 people. Rather than being biodegradable, plutonium destroys biological properties.

In 1972 the .U.S. Occupational Safety and Health Administration ruled that the asbestos level in the work place should be lowered to 2 fibers per cubic centimeter of air, but the effective date of the ruling has been delayed until now. The International Federation of Chemical and General Workers’ Unions report that the 2-fiber standard was based primarily on one study of 290 men at a British asbestos factory. But when the workers at the British factory had been reexamined by another physician, 40--70 percent had X-ray evidence of lung abnormalities. According to present medical information at the factory in question, out of a total of 29 deaths thus far, seven were caused by lung cancer. An average European or American worker comes into contact with six million fibers a day. "We are now, in fact, finding cancer deaths within the family of the asbestos worker," states Dr. Irving Selikoff, of the Mount Sinai Medical School in New York.

It is now also clear that vinyl chloride, a gas from which the most widely used plastics are made, causes a fatal cancer of the blood-vessel cells of the liver. However, the history of the research on vinyl chloride is, in some ways, more disturbing than the "Watergate cover- up. " "There has been evidence of potentially serious disease among polyvinyl chloride workers for 25 years that has been incompletely appreciated and inadequately approached by medical scientists and by regulatory authorities," summed up Dr. Selikoff in the New Scientist. At least 17 workers have been killed by vinyl chloride because research over the past 25 years was not followed up. And for over 10 years, workers have been exposed to concentrations of vinyl chloride 10 times the "safe limit" imposed by Dow Chemical Company.

By "ecocide" the author most probably means()

A. waste utilization

B. ecological balance

C. radioactive reaction

D. massive bio-destruction

题型:选择题

在思想品德课上,七(5)班的同学对如何正确认识自己发表了各自的看法:

王建:“认识自己太容易了,自己都不了解自己,谁还了解自己?”

李路:“认识自己并不容易,当局者迷,旁观者清。自己的问题自己不一定看得清楚。”

马超:“对,正确认识自己不容易,要想对自己有一个全面的、深刻的认识,必须掌握一定的方法,否则就很难做到。”

对于同学们的不同见解,班长刘宝运用自己所学的知识谈了自己的看法,得到了同学们的一致赞同。

(1)你赞同上面三个同学中哪一个的观点?

_______________________________________________________________________________

(2)你认为班长刘宝会运用哪些知识来谈自己的看法?

_______________________________________________________________________________

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劳动法律关系变更

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矿山安全技术

按其组成成分,煤矿粉尘主要分为煤尘和( )。

A.硅铁粉

B.游离二氧化硅

C.岩尘

D.呼吸性粉尘

题型:选择题

业主单位授予监理单位的权力,应明确反映在()中,据此项目监理机构才能开展监理活动。

A.监理合同

B.监理大纲

C.监理规划

D.监理计划

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