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
The ‘a’ wave in venous waveform is absent in case of 
Select and explain. 
A. AV dissociation, B. Atrial fibrillation, C. Tricuspid incompetency, D. All of the above
B: Atrial fibrillation
Answer: B: Atrial fibrillation 
Explanation: None