Final answer:
Anselm responded to Gaunilo's critique by refuting his objections, emphasizing that his ontological argument applies uniquely to necessary beings rather than contingent ones like an island.
Step-by-step explanation:
Anselm's response to Gaunilo was A) He refuted Gaunilo's objections. Gaunilo, a monk who was a contemporary of Anselm, criticized the ontological argument by proposing an analogy of a perfect island, suggesting that the logic used by Anselm could be used to prove the existence of anything defined as the most perfect.
Anselm replied by pointing out that his argument applies only to necessary beings, which exist in every possible world, unlike contingent beings such as an island which do not carry the same necessity.
Anselm's ontological argument rests on the distinction between necessary and contingent existence, claiming that God, a necessary being, must exist by the very nature of his definition.