This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Anatomy
[{'content': 'Passavants ridge is formed by \nSelect and explain. \nA. Palatoglossus, B. Superior constrictor, C. Salpingopharyngeus, D. Palatopharyngeus', 'role': 'user'}, {'content': "Answer: D \nExplanation: Some of the upper fibres of the palatopharyngeus pass circularly deep to the mucous membrane of the pharynx and form a sphincter internal to the superior constrictor. These fibres constitute Passavant's muscle which on contraction raises a ridge called the Passavant's ridge on the posterior wall of the nasopharynx. When the soft palate is elevated it comes in contact with this ridge, the two together closing the pharyngeal isthmus between the nasopharynx and the oropharynx. Ref: BD Chaurasia's HUMAN ANATOMY, Volume 3, 4th edition.", 'role': 'assistant'}]