Final answer:
The correct option is a. Keats compares himself to Cortez to emphasize his awe and longing for new discoveries, mirroring the feelings experienced during exploration.
Step-by-step explanation:
Keats compares himself to "stout Cortez" in the poem to emphasize his longing for exploration and the sense of awe and wonder that comes with discovering something new.
The comparison is drawn to convey the surprise and amazement that Cortez and his men felt upon seeing the Pacific Ocean for the first time, mirroring Keats' own feelings of discovery as he experiences the world of poetry and imagination. This instance in Keats' work underlines the powerful emotions that accompany the act of exploration, whether it be of new lands or intellectual pursuits.