The correct option is the third one, "Nestor and Menelaus welcome Telemachus, offering him food and rest without even knowing his identity".
Xenia was a fundamental Greek principle, which dictated that every guest should be treated with the utmost hospitality, regardless of his origins or filiations. Xenia consists of a reciprocal relationship, in which there must be respect from the host to the guest, as well as respect from the guest to the host. This generosity was expressed in a material way, through the giving of gifts, as well as in a non-material way, by providing shelter and protection.
Therefore, Nestor and Menelaus show the concept of xenia by offering Telemachus food and rest without questioning.