This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ECG and Arrhythmia 2, Subject name: Medicine
[{'content': 'Comment on the diagnosis of the ECG tracing shown below. \nSelect and explain. \nA. First degree AV block, intranodal, B. Second degree AV block type1, intranodal, C. Second degree AV block type 2, infranodal, D. Third degree AV block', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Symmetry in PR interval before and after the missed beat --> Indicating Second degree AV block type 2: infranodal. In Second degree AV block type 1 --> Serial lengthening of PR interval before and after the missed beat. In Third degree AV block --> complete dissociation b/w atria and ventricles.', 'role': 'assistant'}]