<s>[INST] context: Torus tubarius is the tubal elevation in the lateral wall of nasopharynx. It is formed by cartilage of eustachian tube.Rathke s pouch is clinically represented by a dimple above the adenoids. It is the site of buccal invagination to form anterior lobe of pituitary. Craniopharyngioma arises from it.Pharyngeal bursa is a median recess in the adenoid mass lined by epithelium. During development notochord is attached to pharyngeal epithelium which pulled posteriorly towards basiocciput. When infected, this epithelial-lined space forms an abscess called Thomwaldt's disease.Notochord, the remnants of which are represented by nucleus pulposus in intervertebral disc, gives rise to chordoma. Cranially notochord extends through basiocciput and ends caudal to hypophysis thus explaining occurrence of chordoma in clivus.Course of notochord. It runs in the centre of vertebral bodies, enters occipital bone, running dorsal to ventral and lies close to pharyngeal epithelium. It re-enters the base of skull and ends caudal to hypophysis. Remnants of notochord give rise to chordoma. [/INST] question: Nasopharyngeal chordoma originates from: | options: A: Torus tubarius B: Rathke's pouch C: Notochord D: Pharyngeal bursa | answer: C </s>