The Case in Point on the Oil Extraction Suggests That

The Case in Point on the oil extraction suggests that one reason oil may become more costly is that :

A) we will have to give up more and more valuable alternatives to extract oil.
B) speculation is likely to drive up oil prices.
C) oil producers are likely to become more greedy in the future.
D) actually, the Case suggests that oil extraction is likely to become less costly and the future.