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 not affected by: \nSelect and explain. \nA. Heart rate, B. Peripheral resistance, C. Systolic blood pressure, D. Venous return', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]