B

The area between the oblique fibers of the thyropharyngeus and the transverse fibers of the cricopharyngeus (Killian’s dehiscence) lacks muscular reinforcement, making it the structurally weakest part of the pharyngeal wall and the usual site of Zenker’s (pharyngoesophageal) diverticulum formation [Chaplin, 1994, PMID 8010924].