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
A patient of rheumatic heart disease with mitral stenosis and atrial fibrillation is on oral warfarin. On one OPD visit, his INR is found to be 6. What is the action to be taken? 
Select and explain. 
A. Stop warfarin, and review, B. Stop wairfarin, and administer fresh frozen plasma, C. Stop warfarin, and administer intramuscular vitamin K, D. Stop warfarin, and administer intramuscular vitamin K
A: Stop warfarin, and review
Answer: A: Stop warfarin, and review 
Explanation: None