This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and paranasal sinuses, Subject name: ENT
[{'content': 'The antrochoanal polyp is? \nSelect and explain. \nA. Single and grows posteriorly, B. Multiple, C. Bleeding, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Antrochoanal polyp is usually single and unilateral. More tendency to grow posteriorly and do not bleed. Unilateral nasal obstruction is the presenting symptom. Obstruction may become bilateral when polyp grows posteriorly into the nasopharynx and stas obstructing the opposite choana. (Ref - PL DHINGRA diseases of ear nose and throat, 7th edition, page no 193)', 'role': 'assistant'}]