问一道逻辑题，希望大虾帮帮我！

小资y

Twenty years ago, Balzania put in place regulations requiring operators of surface mines to pay for the reclamation 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.

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.

滨崎步祝

答案呢？

ken121222

IMO, C
提供了一个减少cost的途径。

BTW,楼主提问题最好能将不懂的地方有针对性地提出来，这样解答也能更有针对性些。

小资y

ken121222 发表于 2013-7-6 20:53
IMO, C
提供了一个减少cost的途径。

好。主要我题目和选项都不太明白...可以解释下马

xiqiong

政策要求对挖出来的土收费。采煤技术没变，但交的费少了（第一年估计是没办法停止正在进行的工程）

答案是说采煤场选址在好挖的地方了。土量自然就少了！

ken121222

xiqiong 发表于 2013-7-7 07:13
政策要求对挖出来的土收费。采煤技术没变，但交的费少了（第一年估计是没办法停止正在进行的工程）

答案是 ...

楼上正解

云游

Question here is asking us to address a paradox in the reasoning: average reclamation cost rises while the reclamation technology has not improved!

So prephrase: there must be some other factors contribute to the reduction of average reclamation cost！

Read through the choices-- A,B,D,E have provided nothing to address the paradox! Only C point out another cause that might instigate the reduction. Since average reclamation cost is gauged by dividing the total reclamation cost with the number of reclaimed mines, if the high reclamation cost mines are closed, we will surely expect that the average reclamation cost will  drop.