This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ECG, Subject name: Physiology
[{'content': 'A 65-year-old man had an ECG at a local emergency after a biking accident. His weight was 80 kg, and his blood pressure was 160/90 mm Hg. The QRS voltage was 0.5 millivolt in lead I and 1.5 millivolts in lead III. What is the QRS voltage in lead II? \nSelect and explain. \nA. 0.5 millivolt, B. 1.0 millivolt, C. 1.5 millivolts, D. 2.0 millivolts', 'role': 'user'}, {'content': "Answer: D \nExplanation: Einthoven's law states that the voltage in lead I plus the voltage in lead III is equal to the voltage in lead II, i.e. II = I + III which in this case is 2.0 millivolts", 'role': 'assistant'}]