The correct answer is Athena informs him that his father could be alive.
Indeed, the goddess Athena visits Telemachus and tells him that his father might be alive and that he needs to embark on a journey in order to gather evidence of his whereabouts. Athena takes the appearance of King Mentes of the Thapians in order to do that. Telemacchus goes to Pylos and then to Sparta, where King Menelaus reveals the prophecy of Proteus concerning Odysseus return to Ithaca.
Telemachus returns to Ithaca and encounter s beggar who later is revealed to be his father in disguise. Together they plot to kill the suitors and they ultimately liberate their home and avenge all the years of abuses under their hands.