This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Airway, Subject name: Anaesthesia
[{'content': 'Appropriate size of oropharyngeal airways is measured from ? \nSelect and explain. \nA. Incisor teeth to tragus of the ear, B. Corner of mouth to angle of mandible, C. Tip of nose to angle of mandible, D. Ala of nose to angle of mandible', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Oropharyngeal airway Guedel oropharyngeal airway (used to lift the tongue above oropharynx) Take either from the midpoint of the incisor or corner of the lip to angle of the mandible Used in unconscious person; as laryngospasm can occur in conscious person by its use', 'role': 'assistant'}]