This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory, Subject name: Medicine
[{'content': 'Alpha antitrypsin deficiency causes: \nSelect and explain. \nA. Centrilobular emphysema, B. Pan acinar emphysema, C. Lung cyst, D. Bronchiectasis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans: bRef: Robbins, 3rd ed, p. 718, 719', 'role': 'assistant'}]