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: Surgery
[{'content': 'The head tilt procedure while dealing with an unconscious patient in dental chair is done to ensure \nSelect and explain. \nA. Patent airway, B. Blood circulation to the brain, C. To clear the foreign body obstacle, D. To relieve spasm of respiratory muscles', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]