The best response that describes the hero archetype in literature, particularly as it applies to Sir Gawain in "Sir Gawain and the Green Knight," is:
It signifies a character that is clever, resilient, and that faces great challenges.
This choice captures the essence of Gawain's character as he volunteers to take on the Green Knight's challenge, showcasing his bravery and willingness to confront formidable obstacles, which are key traits of a hero.