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': "Einthoven's triangle, what is the value of lead III when lead I = 2 mv and Lead II =1 mv \nSelect and explain. \nA. 1, B. 2, C. 3, D. 4", 'role': 'user'}, {'content': "Answer: A \nExplanation: According to Einthoven's triangle, \xa0voltage in I + III = voltage in II\nSo Voltage in III = II-I\n= 1-2\xa0= -1\nThe value is 1.", 'role': 'assistant'}]