The answer choice that best describes Robert's character development over the course of the novel is:
He remains compassionate and caring without changing significantly.
Throughout "The Awakening," Robert remains a character who expresses care and affection towards Edna Pontellier but does not fundamentally change in his approach to love and commitment. Despite his feelings for Edna, he struggles with societal expectations and ultimately does not pursue a deeper relationship, indicating an internal consistency in his character traits.