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