OG5 阅读 Q26

Choice C is the best answer. The passage makes it clear that while both conventional and organic farming need nitrogen for plant growth, conventional farming uses synthetic fertilizers and organic does not: "Conventional agriculture makes use of 171 million metric tons of synthetic fertilizer each year, and all that nitrogen enables much faster plant growth than the slower release of nitrogen from the compost or cover crops used in organic farming" (lines 61-65,"to...farming"). 
Choice A is incorrect because the passage does not state that conventional and organic farming are equally sustainable and does state that organic farming needs "more land" to produce "fewer crops" (lines 42-43,"agriculture...organic") but does not indicate that it always requires dramatically more land. Choice B is incorrect because the passage does not state that organic farming uses artificial chemicals. Choice D is incorrect because the passage mentions nitrogen runoff only as a product of conventional farming, not organic farming, and does not indicate that only the nitrogen in conventional fertilizers is dangerous.