In free-trade countries such as the United States, even if there is a

It's a strange question, because the stem really doesn't tell us anything. It uses some jargon to say "when international coal prices go up, countries compare international prices and domestic prices when deciding how much international coal to buy". Well of course they do, unless they're locked into contracts with international coal suppliers.

Really all we need is the question, not the preamble: if countries want to be less affected by spikes in international coal prices, what should they do? They can either ensure they have a more reliable supply of domestic coal, or they can use less coal altogether. It seems to me we need to make several assumptions to make any answer work here -- A, for example, is a good answer if we assume that "constant amount" is low or zero, and that domestic suppliers will be able to provide the coal the country needs. That's a lot of assumptions. D seems like the best answer, but I still don't like it very much; the problem with D is that we have no way to know how successful conservation efforts can be, so no way to know if this policy would be sufficiently helpful.