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 cost 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 rears ago, a greater percentage of the coal mined in Balzania today comes from surface mines.
天山pdf的檔我轉不出來,只能用打的嗎?,真累人

這題答案是C,但是這個答案能夠解釋什麼嗎?真搞不懂,再請各位大大幫我看看囉!謝謝啦!
可能是我對這個句話的解讀有錯,以下是我的翻譯,翻的很爛請見諒!
"在Balzania這個鬼地方的山區採礦人已經停止了表面的採礦,因為煤礦每噸reclamation的成本實在是太高了"