Final answer:
Female cannibalism of males during mating can occur to ensure that in situations where females are scarce, no eggs are wasted, and successful mating is more likely with resource-providing males.
Step-by-step explanation:
The question asks about the reasons why females sometimes cannibalize males during or after copulation in certain species. While several hypotheses exist to explain this behavior, options a, b, and d do not align with this behavior's reproductive advantages. Instead, the mate rejection hypothesis suggests that in populations where females are scarce, such behavior ensures that no eggs are wasted, as males could mate with multiple females, leaving some without enough resources. This supports the idea that cannibalism ensures successful mating with those males providing enough resources, thus potentially increasing offspring survival.