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': 'Abnormal function of epithelial chloride channel protein is the cause of \nSelect and explain. \nA. Ehlers Danlos syndrome, B. Marfan syndrome, C. Cystic fibrosis, D. Diabetes insipidus', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]