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
Abnormal function of epithelial chloride channel protein is the cause of 
Select and explain. 
A. Ehlers Danlos syndrome, B. Marfan syndrome, C. Cystic fibrosis, D. Diabetes insipidus
C: Cystic fibrosis
Answer: C: Cystic fibrosis 
Explanation: None