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': 'In the setting of G-proteins which of the following is considered a third messenger : \nSelect and explain. \nA. cAMP., B. Calcium., C. CO., D. NO.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Calcium is considered as a third messenger.', 'role': 'assistant'}]