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: Pharmacology
[{'content': 'Linaclotide is a \nSelect and explain. \nA. Chloride channel activator, B. CFTR blocker, C. Somatostatin antagonist, D. Guanylate cyclase agonist', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Linaclotide is a Guanylate cyclase - C agonist that increases levels of cGMP and stimulates secretion of chloride & bicarbonate ions into the intestinal lumen. It is used in treatment of IBS with constipation.', 'role': 'assistant'}]