Answer:
The answer is indeed letter C. Mathilde's discontent with her humble lifestyle.
Step-by-step explanation:
This excerpt from Guy de Maupassant's The Diamond Necklace makes it very clear that the character, Mathilde Loisel, is truly miserable when it comes to her financial situation in life. She longs for fine clothes, a bigger house, fancier decoration and so on. Even though she and her husband are not poor, she finds it mortifying to watch the ugliness of the things that surround her. She has great taste, but no money to acquire it:
She was distressed at the poverty of her dwelling, at the bareness of the walls, at the shabby chairs, the ugliness of the curtains. All those things, of which another woman of her rank would never even have been conscious, tortured her and made her angry.