This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: COPD and Asthma, Subject name: Medicine
[{'content': 'Increased Reid index is classically associated with? \nSelect and explain. \nA. Chronic Bronchitis, B. Emphysema, C. Bronchiectasis, D. Interstitial lung disease', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The diagnostic feature of chronic bronchitis in the trachea and larger bronchi is enlargement of the mucus secretinggland . The magnitude of the increase insize is assessed by the ratio of the thickness of the submucosal gland layer to that of the bronchial wall (the Reid index--normally 0.4). Chronic smoking causes submucosal gland hyperophy and hyperplasia, leading to a Reid Index of >0.5 indicating chronic bronchitis.', 'role': 'assistant'}]