This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
[{'content': 'All are true about chronic bronchitis except \nSelect and explain. \nA. Cough > 2months, B. Hoover sign is seen, C. Haemoptysis, D. Bronchorrhea', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Chronic bronchitis clinically defined as cough with sputum on most days for 3 consecutive months of 2 successive years. Hoovers sign seen in copd (inward movement of rib cage on inspiration with flat functioning diaphragm.', 'role': 'assistant'}]