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: Medicine
[{'content': 'When P-R interval in a bipolar limb lead Electrocardiograph prolongs beyond 0.20 seconds the patient has \nSelect and explain. \nA. Third degree complete block, B. Second degree Type 2 block, C. First degree complete block, D. Second degree incomplete block', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]