来到逻辑开开胃啊

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?

1. 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.

2. 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.

3. 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.

4. 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.

5. As compared to twenty years ago, a greater percentage of the coal mined in Balzania today comes from surface mines.

   这题是什么意思 谁能解释下？？

"reclamation" means rehabilitation of disturbed areas resulting from surface or underground mining. The basic objective of reclamation at mines is to reestablish the vegetative cover, soil stability, and water conditions at the site. As a second beneficial use, mines are reclaimed for fish and wildlife, grazing, forestry, wetlands, and commercial and industrial uses.

废矿回填/改建。

Is C the correct answer?