I think the answer is D.
Less than 50 percent of a certain tropical country’s wildlands remains intact. Efforts are under way to restore biological diversity in that country by restoring some destroyed wild habitats and extending some relatively intact portions of forests. However, opponents argue that these efforts are not needed because there is still plenty of wildland left.
The argument says that wildland is decreasing and effort should be made to preserve the biological diversity of the country. Efforts are being made in this direction by restoring the destroyed wildland and extending the available wildland. The opponents are saying this effort is not needed because enough biological diversity exist.
Which of the following, if true, most significantly weakens the argument of the opponents of conservation efforts?
How do we weaken opponent's argument ? One way is to show that available biological diversity might decrease if efforts to increase the wildland are not made. Another way is to show that wildlife ecosystem may decrease if present situation is not remedied. Lets go through options.
(A) As much, if not more, effort is required to restore a wild habitat as to preserve an intact habitat. - this does not address the conclusion. efforts are required to preserve / restore the wild habitat but what if diversity can flourish in diminished land? does this weaken the claim of opponents ? No.
(B) The opponents of restoration efforts are, for the most part, members of the wealthier classes in their own villages and cities. - this is just a throw away option. nothing to comment here really. Just another easy out of scope.
(C) Existing conservation laws have been very effective in preserving biological diversity within the wildlands that remain intact.
- this strengthens the opponent's argument.
(D) For many tropical species native to that country, the tropical wildlands that are still relatively intact do not provide appropriate habitats for reproduction.- if tropical species need different environment to flourish then opponent's argument will be fall flat. because then we will need to develop the wildland conducive to tropical species.
(E) If a suitable population of plants and animals is introduced and is permitted to disperse and grow, tropical habitats can most certainly be restored. - this strengthens the opponent's argument. If a suitable population can be diversified in limited space then we do not need to grow the wildland.
Hence i believe Answer is D.