Final answer:
The Red Queen hypothesis suggests that sexual reproduction is maintained due to the evolutionary arms race with pathogens, which requires constant genetic variation to adapt for survival, aligning with option c.
Step-by-step explanation:
The Red Queen hypothesis explains the persistence of sexual reproduction despite its higher costs compared to asexual reproduction. It suggests that sexual reproduction provides continuous genetic variation which is necessary for populations to adapt and compete in an ever-changing environment with co-evolving species, predators, and pathogens.
According to the hypothesis, the scenario that provides the best support for maintaining sexual reproduction is one where pathogens co-evolve with a host species, applying selection pressure that favors genetic diversity for survival. Therefore, the correct answer to the question is: c. Pathogens of the sexual organism evolve to overcome the organism's defenses. This constant evolutionary arms race prevents any one species from dominating and forces them to evolve continuously, which supports the notion of the Red Queen hypothesis.