Final answer:
Option a is the correct answer. Mutualism is a symbiotic relationship where both organisms benefit and can include defensive benefits, such as the protection provided by clownfish to sea anemones against predators.
Step-by-step explanation:
Mutualisms can indeed aid in defense against enemies, making the statement True. Mutualism is a symbiotic relationship where both species benefit from their interaction. For instance, the clownfish and the sea anemones exhibit mutualism; the clownfish receives protection from predators using the stinging tentacles of the anemone, and in return, it protects the anemone from anemone-eating fish. This relationship also includes an aspect of defense, as the clownfish actively protects the anemone, demonstrating how mutualism can be related to defense mechanisms.