Choice C is the best answer. In the first sentence of the last paragraph of Passage 2, the author expresses reservations about the immediate usefulness of teixobactin: "So, what are my caveats? Well, I see three. First, teixobactin isn't a potential panacea. . . . Secondly, scaling to commercial manufacture will be challenging. . . . And, thirdly . . . teixobactin now faces the long haul of clinical trials." The author uses the word "caveats" to introduce skeptical comments about teixobactin's value. Thus, the word "caveats," as used in the first sentence of the last paragraph of Passage 2, most nearly means misgivings.
Choices A, B, and D are incorrect because in the context of the passage, "caveats" means misgivings, not exceptions (choice A), restrictions (choice B), or explanations (choice D).