This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hematology, Subject name: Pharmacology
Which of the following medications would be prescribed most frequently to patients suffering from chronic atrial fibrillation? 
Select and explain. 
A. Lidocaine, B. Bretylium, C. Warfarin, D. Adenosine
C: Warfarin
Answer: C: Warfarin 
Explanation: Patients of chronic atrial fibrillation are at high risk of developing thromboembolism. Oral anticoagulants are most frequently advised drugs in these patients to decrease the risk of this adverse effect. Warfarin being oral anticoagulant is used as prophylaxis in chronic atrial fibrillations because of propensity of these pts. developing thromboembolism is higher.