Answer is B. He wants to make social connections to help advance his career.
Explanation:
Both Monsieur Loisel and Mathilde are part of the low-income social class and wish to be accepted by the upper-class and, eventually, gather much more money. So he can make his wife change her mind and attend the ball with him, Mrs. Loisel buys her an expensive dress, and she borrows an imitation diamond necklace, the one she looses and latter becomes central to the story's plot.
