Answer:
a) had described Aeneas' journey to the underworld
Step-by-step explanation:
Dante picks Virgil as his guide for the underworld since he realized Dante was a regarded author and trusted individuals would consider his words astutely.
The setting in Dante's story resembles an augmentation of the Aeneid in Virgil's book six of a similar name. So one reason Virgil is fit the bill to control Dante on his plummet through descent is that he had portrayed Aenea's voyage to the underworld.