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: Microbiology
[{'content': 'Cholera toxin - \nSelect and explain. \nA. Increases the levels of intracellular cylic GMP, B. Acts through the receptor the opiates, C. Causes continued activation of adenylate cyclase, D. Inhibits the enzyme phosphodiesterase', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]