Final answer:
Victor Frankenstein spends most of his time at Belrive in isolation, deeply introspective and despairing, corresponding to option D.
Step-by-step explanation:
At Belrive, Victor Frankenstein isolates himself from others and spends most of his hours sinking into deep despair and introspection. This corresponds to option D. Victor becomes consumed by his guilt and the repercussions of his scientific endeavors, particularly the creation of the Monster. The sense of isolation and remorse he feels leads him to distance himself from social interactions and the beauty of the natural world, ultimately trapping him in a cycle of despair and self-reflection.