Explanation
Correct answer: A.
Choice A is the best answer because it presents a statement about the proposed strategy that is consistent with Walker et al.’s position. The strategy involves identifying and disseminating corals with strong heat resistance as a means of mitigating coral mortality during episodes of high heat. According to the text, Walker et al. note that if this trait were “exclusively advantageous,” it would have already spread throughout coral populations—implying that the trait carries some evolutionary cost. The text then provides evidence of this cost: Walker et al. have found that strongly heat-resistant corals display much less growth after heat stress (indicative of reduced thriving) than do moderately heat-resistant corals. Given the apparent trade-off between strong heat resistance and growth after heat stress, Walker et al. would be likely to agree that the strategy entails promoting a trait that protects against high heat but is associated with reduced thriving afterward.
Why the other choices are wrong
Choice B
Choice B is incorrect because the text doesn’t suggest that episodes of high heat are predicted to become infrequent. Also, the text establishes that Walker et al. found that the trait of high heat tolerance is associated with a significant trade-off—reduced growth after heat stress. Given the cost that accompanies strong heat resistance, Walker et al. wouldn’t be likely to agree that the trait is advantageous now.
Choice C
Choice C is incorrect because the text doesn’t discuss the effects of moderate heat on corals or distinguish between corals that are exposed to different levels of heat. The text also doesn’t address the frequency of corals’ exposure to heat. Therefore, there is no basis for concluding that Walker et al. would agree that the strategy benefits corals that are frequently exposed to high heat but harms those that are frequently exposed to moderate heat.
Choice D
Choice D is incorrect because the text doesn’t indicate that heat resistance in corals is poorly understood. On the contrary, Walker et al. present a specific finding about this trait, linking reduced growth after heat stress to strong heat resistance. In addition, the text indicates that strong heat resistance protects corals during episodes of high heat; while their research shows that heat resistance is linked to reduced growth after such episodes, Walker et al. likely wouldn’t agree that it is linked to increased coral mortality during such episodes.