prep一题不会……

lastnight

Twenty years ago, B 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?


我选的是 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.


答案是Mine operators have generally ceased surface mining in the mountainous areas of B because reclamation costs per ton of coal produced are particularly high for mines in such areas.

看不懂啊看不懂啊……

cat19bear

文章说的是 reclaimation cost，和楼主选的 the use of coal as a fuel  没有关系的

答案说的是 因为surface mining  少了 （这种mining 的reclaimation 的cost 比较高），所以支持 问题的 reclaimation cost 的平均值降低