Question

survival of the fittest references animals abilities to

Explanation:

To solve this, we analyze the context: "Survival of the fittest" relates to organisms' ability to adapt and change over time. Among the options, "evolve" means to develop gradually, especially in a biological context of species changing over generations, which fits the idea of animals' abilities tied to survival of the fittest (natural selection and evolution). Other words like "adage" (a saying), "citadel" (a fortress), etc., don't relate to biological change.

"Survival of the fittest" connects to biological evolution. "Evolve" means gradual development, matching animals’ adaptive abilities for survival. Other options are irrelevant to this context.

Answer:

evolve