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': 'Ventricular contraction lasts for: \nSelect and explain. \nA. Beginning of Q wave to end of S wave, B. Beginning of Q wave to the end of T wave, C. Beginning of P wave to end of T wave, D. Beginning of R wave to the end of T wave, if Q wave is absent', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Beginning of Q wave to the end of T wave', 'role': 'assistant'}]