The quotation that best reflects Mathilde's attitude change is:
C. "But sometimes, when her husband was at the office, she sat down by the window and thought of that evening long ago, of the ball at which she had been so beautiful and so much admired." (Paragraph 96)
This quotation illustrates Mathilde's longing for her past life and the contrast between her former desires and her current situation. It captures a sense of nostalgia and reflects how her experiences and hardships have impacted her outlook on life. While other options highlight her struggles and the consequences of her choices, option C emphasizes a significant emotional shift in her attitude as she reflects on what she desires versus what she has become.