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': "Canon 'a' wave is seen in \nSelect and explain. \nA. Junctional rhythm, B. Atrial fibrillation, C. Atrial flutter, D. Ventricular fibrillation", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Junctional rhythm", 'role': 'assistant'}]