求助，GWD-TN-12,T-4-Q2

zhouliang0123

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.
这道题为什么选C啊？题目好像只是说reclamation costs是每吨煤的收费啊？C项也没解释reclamation costs降低的原因啊
reclamation costs我觉得B是对的，需求减少，必然要削减成本啊。

求大神指点指点，完全不知道题目的考点在哪.

脏兮兮

the average reclamation cost for a surface coal mine being reclaimed today is only four dollars per ton of coal that the mine produced
说average reclamation cost下降。。题目就是问为什么平均cost下降。。
C选项就说eclamation cost  particularly high 的已经cease。。那么成本高的停止了，平均成本就下降了。
B选项中coal的用处跟开采成本毫无关系。。。不会因为coal更好用而开采成本越低。
本题的重点还是在average！

hscryzer

Average的意思是隐含前提条件是Average R.Cost = 表面开采所付的环保费/总开拓的煤矿数吧，然后实际上更多的没有从表面开采 分子变小分母不变或者变大，所以Avg decline....

也是有点缺失上下文的推理题不过其他几个选项更错就是了。。。

sasha_wen

讲讲我的理解：
Yet后是关键：现在surface coal/coal的the average reclamation cost 下降为过去的一半，问原因？
Yet前说明了coal的分母不变因为技术没有变，地方还是Balzania这个地方，唯一能变的就只有分子上的surface coal变少才能使得整个分式减少，也就是C，仅供参考！