This is a primary purpose question, as clearly stated in the question.
Correct Answer: (D)
In the beginning of the first paragraph, the traditional firefighting system is argued against by foresters and ecologists for it's detrimental effects on the forest ecosystems. The author sides with the foresters and ecologists and it's apparent in the following paragraphs. The negative consequences of the traditional firefighting system is explained, an alternative to this is presented by example of natural fires, and an element to carry out that alternative is stated.
(A) We aren't exactly told what's "impeding the enactment" of the alternative the author's rooting for. We're just told how it can be used and why it is better.
(B) Almost chose this one. This is wrong because the primary purpose is that one policy is better than the other. We're not just comparing the effects.
(C) Eliminate for the mention of money. There wasn't any mention in the passage.
(D) This is the correct answer. The author recommends this alternative change because the traditional firefighting method was doing more harm than good.
(E) Contradictory goals that are compatible? Nope, we're saying one is better than the other and that the former needs to be implemented.
Hope this helps!