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
Canon 'a' wave is seen in 
Select and explain. 
A. Junctional rhythm, B. Atrial fibrillation, C. Atrial flutter, D. Ventricular fibrillation
A: Junctional rhythm
Answer: A: Junctional rhythm 
Explanation: Ans. is 'a' i.e., Junctional rhythm