OG5 阅读 Q29

Choice D is the best answer. The passage states that conventional agriculture can be superior to organic farming in terms of producing "sheer calories" (line 88,"delivering... staple"). In this context, "sheer" most nearly means pure; the passage is referring to the pure number of calories delivered by foods. 
Choices A, B, and C are incorrect because in the context of discussing the calories foods can provide, "sheer" suggests the pure number of calories. Also, it does not make sense to say that calories can be seen through (choice A), are somehow sudden or happen unexpectedly (choice B), or are at a very sharp angle (choice C).