This would be: C. In the rising action, the narrator hears the valet laughing and whispering in the hallway, which motivates him to attack the valet at the climax.
How to get the action
In Guy de Maupassant's story "An Uncomfortable Bed," the rising action refers to the events leading up to the story's climax, building tension and suspense.
As the plot progresses, the narrator experiences trouble sleeping due to an uncomfortable bed, leading to a sense of unease and restlessness. During this rising action, the narrator becomes increasingly paranoid, especially after hearing the valet's suspicious laughter and whispers in the hallway.