This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics, Subject name: Medicine
[{'content': 'Cause of thick pancreatic secretions in cystic fibrosis? \nSelect and explain. \nA. Overproduction of mucin, B. Failure to clear mucin due to epithelial dysfunction, C. Defect in chloride channel leading to water reabsoption, D. Defect in sodium channel leading to water reabsorption', 'role': 'user'}, {'content': 'Answer: C \nExplanation: CF occurs because of mutations in the gene that makes a protein called CFTR (cystic fibrosis transmembrane regulator). A person with CF produces abnormal CFTR protein -- or no CFTR protein at all, which causes the body to make thick, sticky mucus instead of the thin, watery kind. This blockage causes a drop in the amount of digestive enzymes the pancreas puts out. Because of this, a child with CF has trouble absorbing fats, some proteins, and fat-soluble vitamins A, D, E, and K. The problems with the pancreas can get very severe. Some of the hormone cells in the pancreas can be destroyed Ref Robbins 9/e pg 178', 'role': 'assistant'}]