It would be A, the other choices simply doesn't fit with what you are trying to provide to the reader. You want to pull them in
Gawain wears the green girdle as a symbol of his weakness. He behaved deceitfully and returned to Camelot bearing the girdle as a symbol of his failure in keeping his vow.
Percy, Annabeth, and Grover are good friends. They trust each other and respect each other. Each one would lay down his or her life to save the other.