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 3, Subject name: Medicine
Most common arrhythmia: 
Select and explain. 
A. Inappropriate sinus tachycardia, B. Junctional premature complexes, C. Atrial fibrillation, D. Atrial flutter
C: Atrial fibrillation
Answer: C: Atrial fibrillation 
Explanation: None