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': 'Genetic risk factor for COPD is \nSelect and explain. \nA. a1 Antitrypsin Deficiency, B. Cystic fibrosis, C. Marfan syndrome, D. Severe combined immunodeficiency', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Severe a1 Antitrypsin deficiency is a proven genetic risk factor for COPDAlthough only approximately 1% of COPD patients are found to have severe a1AT deficiency as a contributing cause of COPD, these patients demonstrate that genetic factors can have a profound influence on the susceptibility for developing COPDSpecific treatment in the form of a1AT augmentation therapy is available for severe a1AT deficiency as a weekly IV infusion Patients with cystic fibrosis develop bronchiectasisRef: Harrison 19e pg: 1704', 'role': 'assistant'}]