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': 'The laryngeal mask airway allows positive pressure ventilation with maximum pressure of:- \nSelect and explain. \nA. 10 cm H2O, B. 20 cm H2O, C. 30 cm H2O, D. 40 cm H2O', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The LMA allows a positive pressure of 20 cm of H2O for ventilation .', 'role': 'assistant'}]