标题: 求助一道题！GMAT逻辑 prep里的：Twenty years ago, Balzania put in place regulations requirin [打印本页] 作者: kykykykyno 时间: 2017-9-22 17:00 标题: 求助一道题！GMAT逻辑 prep里的：Twenty years ago, Balzania put in place regulations requirin 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.
A 该国家煤矿比任何其他国家的煤矿是更便宜开采的。不是和其他国家比，是25年前和25年后比
B 更少的煤被用作燃料。不能解释
C 旷工现在已经停止山区的表面开采，因为每吨煤的开采费太高了。那对于山区的表面煤矿，停止开采意味着不用交开采费，所有表面煤矿的总开采成本减少，但煤的总吨数没有变化。所以单个表面煤矿的平均开采成本减少
D 表面煤矿比地下煤矿生产成本更低的煤。不是表面煤矿和地下煤矿比较
E 现在更多的煤来自表面煤矿。和开采成本变化没有关系，不能解释作者: 典座 时间: 2020-8-2 13:53
C说，矿主终止了山上的表面矿，因为复耕费用在这里特别高。
这里其实就是简单的Price=cost+profit。如果成本降低了（取消山里表面矿的开采），那么profit不变的情况下，price自然会降低。
