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': 'Which of the following always indicates obstruction to the airway? \nSelect and explain. \nA. Slow pounding pulse, B. Strenuous breathing, C. Increase in pulse rate, D. Decrease in blood pressure', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]