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
Patients with atrial fibrillation have 
Select and explain. 
A. Regular irregular pulse, B. Irregularly irregular pulse, C. Anacrotic pulse, D. Pulsus alternans
B: Irregularly irregular pulse
Answer: B: Irregularly irregular pulse 
Explanation: None