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: Medicine
[{'content': 'True statements about emphysema -a) Breathlessness is always thereb) Diffusion rate for carbon monoxide is reducedc) Restrictive pattern of lung diseased) Long-term bronchodilator therapy is not effective \nSelect and explain. \nA. acd, B. abd, C. abc, D. ab', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]