This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Anterior two third of the tongue is demarcated from the posterior one third by: plexus, 2-long thoracic plexus, 2-long thoracic 
Select and explain. 
A. Passavant's ridge, B. Sulcus terminalis, C. Circurnvallatepapillae, D. Filifonn papilla
B: Sulcus terminalis
Answer: B: Sulcus terminalis 
Explanation: Ans: B. Sulcus terminalis(Ref Gray's 41/e p5 I I, 40/e p503)Anterior two third of the tongue is demarcated from the posterior one-third by sulcus terminalis.Tongue:Divided by a V-shaped sulcus terminalis.Fuher divides tongue into,Anterior, oral (presulcal) pa facing upwards.Posterior, pharyngeal (postsulcal) pa facing posteriorly.Anterior pa forms about two-thirds of tongue length.