This doesn’t explain why the need for preservation outstrips the available funding. Even if (A) is true, we know that this funding has nevertheless increased at a faster rate than the land area in need of preservation. We must explain why more money is still needed.

The available funding has also increased at a rate much higher than inflation. For (B) to be an adequate explanation, it would need to suggest that salary growth has outstripped the funding increase and that those salaries are a significant draw on that funding.

This doesn’t explain why the available funding is insufficient. Even if wetlands are more proactively identified for preservation, the fact remains that funding has increased at a faster rate than the land area in need of preservation. Why is that funding still not enough?

This doesn’t explain why the available funding for wetlands is insufficient. Even if (D) is true, we know that funding for wetlands has effectively tripled. The correct answer must explain why even that amount of money is not enough.

If the amount of funding was very small to begin with, then even a tripling of that amount is still a small amount. Meanwhile, the total wetland area in need of preservation was large to begin with and is now twice that size. So, the amount of funding has always been too little.