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【单选题】
At the present time, 98 percent of the world energy consumption comes from stored sources, such as fossil fuels or nuclear fuel. Only hydroelectric and wood energy represent completely renewable sources on ordinary time scales. Discovery of large additional fossil fuel reserves, solution of the nuclear safety and waste disposal problems, or the development of controlled thermonuclear fusion will provide only a short-term solution to the world's energy crisis. Within about 100 years, the thermal pollution resulting from our increased energy consumption will make solar energy a necessity at any cost. Man's energy consumption is currently about one part in ten thousand that of the energy we receive from the sun. However, it is growing at a 5 percent rate, of which about 2 percent represents a population growth and 3 percent a per capita energy increase. If this growth continues, within 100 years our energy consumption will be about 1 percent of the absorbed solar energy, enough to increase the average temperature of the earth by about one degree centigrade if stored energy continues to be our predominant source. This will be the point at which there will be significant effects in our climate, including the melting of the polar ice caps, a phenomenon which will raise the level of the oceans and flood parts of our major cities. There is positive feedback associated with this process, since the polar ice cap contributes to the partial reflectivity of the energy arriving from the sun: As the ice caps begin to melt, the reflectivity will decrease, thus heating the earth still further. It is often stated that the growth rate will decline or that energy conservation measures will preclude any long-range problem. Instead, this only postpones the problem by a few years. Conservation by a factor of two together with a maintenance of the 5 percent growth rate the problem by only 14 years. Reduction of the growth rate to 4 percent postpones the problem by only 25 years in addition, the inequities in standards of living throughout the world will provide pressure toward an increase in growth rate, particularly if cheap energy is available. The problem of a changing climate will not be evident until perhaps ten years before it becomes critical due to the nature of an exponential growth rate together with the normal annual weather variations. This may be too short a period to circumvent the problem by converting to other energy sources, so advance planning is a necessity. The only practical means of avoiding the problem of thermal pollution appears to be the use of solar energy. (Schemes to 'air-condition' the earth do not appear to be feasible before the twenty-second century. ) Using the solar energy before it is dissipated to heat does not increase the earth's energy balance. The cost of solar energy is extremely favorable now, particularly when compared to the cost of relocating many of our major cities. The author is primarily concerned with ______.
A.
describing a phenomenon and explaining its causes
B.
outlining a position and supporting it with statistics
C.
isolating an ambiguity and clarifying it by definition
D.
presenting a problem and advocating a solution for it
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参考答案:
举一反三
【判断题】电化学反应可以没有物质的化学变化。( )
A.
正确
B.
错误
【单选题】某同学梳理归纳了以下知识: 1中和反应属于复分解反应 2组成元素相同的物质性质一定也相同3除去二氧化碳中的氯化氢气体,可以用氢氧化钠溶液4配制 6% 的氯化钠溶液,称量氯化钠固体时,砝码下面没放纸会使所配制的氯化钠溶液质量分数偏低 5检验氢氧化钠溶液是否变质可以用酚酞溶液6离子是带电的粒子,所以带电的粒子一定是离子。其中正确的个数有
A.
1个
B.
2个
C.
3个
D.
4个
【单选题】在总账系统中设置转账分录时无须定义以下哪一项?
A.
借货方向
B.
摘要
C.
凭证类别
D.
凭证号
【单选题】下列说法中,不正确的是
A.
化学反应中既有物质变化又有能量变化
B.
即使没有发生化学变化,也可能有能量的变化
C.
任何化学反应中的能量变化都表现为热量变化
D.
物质的化学能可以通过不同的变化方式转化为热能、电能等
【判断题】电化学反应可以没有物质的化学变化。
A.
正确
B.
错误
【简答题】int score=int.Parse(Console.ReadLine()); if(score>=60) Console.WriteLine("考试通过!"); else Console.WriteLine("考试不通过!"); 简单描述上面代码实现的功能:
【判断题】蝶蛾类昆虫的成虫都是虹吸式口器
A.
正确
B.
错误
【单选题】如图所示的具有大平面铸件的几种分型面和浇注位置方案中,合理的是( )。
A.
B.
C.
D.
D
【单选题】下列说法正确的是(  )
A.
一个水分子由一个氧元素和2个氢元素构成
B.
参加化学反应的各物质在反应前后,元素的种类和原子的个数都没有变化
C.
在化学反应中分子可分成原子,所以分子比原子大
D.
氢气燃烧生成水和电解水的基本反应类型相同
【单选题】如图 所示的具有大平面铸件的几种分型面和浇注位置方案中,合理的是
A.
A处
B.
B处
C.
C处
D.
D处
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