Carotenoids, a family of natural pigments, form an important part of the colorful signals used by many animals. Animals acquire carotenoids either directly (from the plants and algae that produce them) or indirectly (by eating insects) and store them in a variety of tissues. Studies of several animal species have shown that when choosing mates, females prefer males with brighter carotenoid- based coloration. Owens and Olson hypothesize that the presence of carotenoids, as signaled by coloration, would be meaningful in the context of mate selection if carotenoids were either rare or required for health. The conventional view is that carotenoids are meaningful because they are rare: healthier males can forage for more of the pigments than can their inferior counterparts. Although this may be true, there is growing evidence that carotenoids are meaningful also because they are required: they are used by the immune system and for detoxification processes that are important for maintaining health. It may be that males can use scarce carotenoids either for immune defense and detoxification or for attracting females. Males that are more susceptible to disease and parasites will have to use their carotenoids to boost their immune systems, whereas males that are genetically resistant will use fewer carotenoids for fighting disease and will advertise this by using the pigments for flashy display instead.
【OG19-P384-443题】According to "the conventional view" referred to in highlighted text of the passage, brighter carotenoid-based coloration in certain species suggests that an individuall
④ 证据表明， carotenoids有利于健康
根据Conventional view定位到文中The conventional view is that carotenoids are meaningful because they are rare: healthier males can forage for more of the pigments than can their inferior counterparts.明确指出健康的雄性可以获得更多的pigment，也就是carotenoids，它们具有更高的获取能力，D选项正确。
难道选C是因为The conventional view 是rare而不是healthy，所以不能选superior immune system ？
我选择错误选项D的原因是最后一句： males that are genetically resistant will use fewer carotenoids for fighting disease and will advertise this by using the pigments for flashy display instead. 免疫力强了，就可以把更多的pigments用于display coloration 之类的了。为什么这样想是错误的？求教，谢谢。
【OG19-P384-444题】The idea that carotenoid-based coloration is significant partly because carotenoids are required for health suggests that a lack of bright coloration in a male is most likely to indicate which of the following?