C. The author likens joy to sunshine to show how positive feelings can overcome dreariness.
Explanation:
This is a very common metaphor in literature: Sunshine is like an almighty force that can overcome pretty much anything.
In this case, Hector's joy is compared to sunshine, and there's no literal sunshine actually involved. Regardless, the figurative brightness and warmth of Hector's positive attitude is told to be powerful enough to overcome the dreariness (likened to gray skies and rain) that those around him may be going through.
The answer is D because it is the only answer choice that actually points out Hector's attitude as being a sunshine that overcomes the dreariness in others' moods.
