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: Physiology
[{'content': 'Cardiac output is a measure of: \nSelect and explain. \nA. Peripheral resistance X tissue fluid, B. Peripheral resistance X cardiac rate, C. Blood pressure X cardiac rate, D. Heart rate X blood volume', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]