Which is a theme of the Iliad? A. No one, no matter how strong, is invulnerable. B. Great heroes never hesitate or falter. C. Seeking vengeance is cowardly and foolish. D. Justice always topples tyranny.

A. No one, no matter how strong, is invulnerable.

This is evidenced by the killing of Hector and Achilles, two great warriors, the latter of whom was invincible. Both of them were killed during the course of the war, showing that though they were very strong, they weren't invulnerable.