Choice A is the best answer. The passage makes it clear that "most environmentalists" (line 27,"Of...environmentalists") believe conventional agriculture produces food that is not as healthy as food produced through organic farming and that it is more harmful to the environment than organic farming is: many environmentalists "have embraced organic food as better for the planet—and healthier and tastier, too—than the stuff produced by agricultural corporations" (lines 28-31,"regard... disdain").
Choices B, C, and D are incorrect because they are not supported by the passage. The passage never states that many environmentalists believe that conventional farming reduces the need to convert wilderness to farmland (choice B), is in any way good for the environment (choice C), or protects wildlife habitats (choice D).