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': 'Isovolumetric relaxation is defined as \nSelect and explain. \nA. Relaxation of both atria, B. Relaxation of both atria with all valves open, C. Relaxation of LV with mitral & aortic valve closed, D. All of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: ‘Isovolumetric’ means the volume remains same. That occurs only when both the valves are closed.', 'role': 'assistant'}]