Our goal is to evaluate the farmers' plan to stop producing crops and instead sell their water to other needy farmers (and cities). Generally speaking, these types of problems can be solved by the variance test. That is to say, we can offer opposing answers to each option to determine whether this information would be useful.

For example, let us take answer choice A. Let us suppose "Yes, water prices will remain subsidized in the future." In no way does this offer useful information to the farmers as to whether they should sell their water now.

But the real question posed is how to determine between B and D. Let us first examine B. Let us suppose that we say "Yes, produce prices will increase if the farmers let their crops die and instead sell their water." At first you might think that this is relevant. However, if the farmers sell their water, they will not have access to the higher produce prices. On the other hand, if they don't sell their water, there will be no higher produce prices to take advantage of. In either situation, the farmers will be unable to benefit from the theoretical higher produce prices. Accordingly, it is information that should not guide their choice.

D, on the other hand, is relevant. Imagine that we say "Yes, farmers can easily replant their crops next year." If so, then they can easily take advantage of the water prices. If, on the other hand, we answer "No, they cannot easily replant next year. The trees will take several years to grow big enough to generate a profitable produce harvest" then we can see that selling the water is a bad idea. Therefore, D is useful information and the best answer.