Final answer:
Sir Gawain is offered a green girdle by the lady of the castle, which is meant to protect him, signifying a test of his morals in the Arthurian legends.
Step-by-step explanation:
Sir Gawain cannot resist temptation when the lady of the castle offers him a green girdle that supposedly will protect him. This event is a pivotal moment in the Arthurian legends where Gawain's moral fortitude is tested. The green girdle represents not only physical protection but also serves as a symbol of Gawain's encounter with temptation and his subsequent moral dilemma. This narrative is a common exploration in chivalric romance, often highlighting the complexity of human virtues and vices.