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
Crofelemer is a 
Select and explain. 
A. Chloride channel activator, B. CFTR blocker, C. Somatostatin antagonist, D. Guanylate cyclase agonist
B: CFTR blocker
Answer: B: CFTR blocker 
Explanation: Crofelemer blocks CFTR and chloride channels and is approved for relieving symptoms of diarrhoea is AIDS patients on antiretroviral therapy.