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': 'In the small intestine, cholera toxin acts by- \nSelect and explain. \nA. ADP ribosylation of the G regulatory protein, B. Inhibition of adenyl cyclase, C. Activation of GTP ase, D. Active absorption of NaCl', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]