Conclusion: Do not worry about the mole rodent.
(A) The birds of prey capture and kill every single Spotted Mole that comes above ground. - what about those that remain underground? These rodents can still pose a significant threat to the farmers' crops.
(B) Some land-based mammals active in this region, such as fox, will also hunt and eat the Spotted Mole on a regular basis. - (B) could certainly be a candidate for the right answer to this question. But, (B) does not tell us whether these land based mammals have the capability to kill the spotted mole that live underground, other than those moles that expose themselves to these mammals on land.
(C) No other animal could pose as significant a threat to the above-ground fruits as could the Spotted Mole. - does not help establish the conclusion.
(D) The times of day the Spotted Mole feeds are the same as the times of day that the birds of prey are in the air. - if the feeding time did not coincide with the flight time of the birds of prey, then we can infer that the spotted mole still pose as a great threat to the farmers' crops. However, if the feeding time does coincide with the flight time of the birds of prey, then we can reasonably infer that the population of the spotted mole will be greatly diminished to the extent that would help protect the farmers' crops. Hence, (D) is the necessary to assume in order to establish the conclusion. Therefore, (D) is the right answer choice.
(E) Larger burrowing mammals, such as badgers or weasels, can dig up the burrows of the Spotted Mole, endangering those that remain underground. - (E) emphasizes on the threat factor faced by spotted mole. However, (E) still does not guarantee that the population of the spotted mole will be low enough for the farmers to not worry about their crops.