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标题: 【请教】T-4-Q2 [打印本页]

作者: hduszj 时间: 2009-7-9 19:08
标题: 【请教】T-4-Q2

T-4-Q2

Twenty years ago, Balzania put in place regulations requiring operators of surface mines to pay for the reclamation（开垦） of mined-out land. Since then, reclamation technology has not improved. Yet, the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulations took effect.

Which of the following, if true, most helps to account for the drop in reclamation costs described?

A. Even after Balzania began requiring surface mine operators to pay reclamation costs, coal mines in Balzania continued to be less expensive to operate than coal mines in almost any other country.

B. In the twenty years since the regulations took effect, the use of coal as a fuel has declined from the level it was at in the previous twenty years.

C. Mine operators have generally ceased surface mining in the mountainous areas of Balzania because reclamation costs per ton of coal produced are particularly high for mines in such areas.（矿的总产量也少了啊——总钱数少了，总产量也少了，并不能推出平均每吨成本就少了啊？？？）

D. Even after Balzania began requiring surface mine operators to pay reclamation costs, surface mines continued to produce coal at a lower total cost than underground mines.

E. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines.

答案：C

请各路大侠指教！！！谢谢！！！

作者: xfi883 时间: 2009-7-10 01:43
注意：the average reclamation cost这句话，实际上是说，在表面开发和其他地方开发的平均费用。如果，在表面开发的成本很高，那么工厂就会去其他地方开发以降低成本。那么，平均开发成本就要低于表面和其他地方同时开发的成本。C选项就是这个意思。

作者: edmundshi 时间: 2009-7-10 17:25

"costs per ton of coal produced are particularly high for mines in such areas"说明山区的平均开发成本高于总平均成本开发成本

总平均成本中较高平均成本的那部分没了，总平均成本不就降低了吗

实在不懂可计算一下，设较高的平均开发成本为8 D/t 占总平均的50%，没撤销高较高开发成本时的总平均开发成本为6D/t，可算得其他的地方平均开发成本为4 D/t，把较高的那部分开发成本去掉，现在的总平均不就变为4 D/t了吗

作者: xfi883 时间: 2009-7-11 00:19
厉害，edmundshi,你数学太好了。

作者: zanyingsan 时间: 2009-10-24 02:10
哦哦哦哦哦哦哦哦~~！！！！

我是用排除法做的，比较笨。

作者: lenovoo 时间: 2010-3-22 22:18
thx

作者: muhuiyun777 时间: 2010-7-9 16:51
我选了B ，咔咔~~~我发现我越想越复杂，但B也有道理哦

作者: hyolangu 时间: 2012-3-22 22:33
同意ls 经济学不是这样的么需求越少了不是价格会下降么

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