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 effects are mediated by stimulation of which of the following second messengers - \nSelect and explain. \nA. cAMP, B. cGMP, C. Ca++ - Calmodulin, D. IP3 / DAG', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]