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
Hypercoagulability and dermal vascular necrosis are early appearing adverse effects of: 
Select and explain. 
A. Clopidogrel, B. Heparin, C. Warfarin, D. Vitamin K
C: Warfarin
Answer: C: Warfarin 
Explanation: Oral anticoagulants inhibit the activation of several clotting factors (II, VII, IX and X) as well as anti-clotting proteins (protein C and S). First to disappear is protein C that can result in hypercoagulation resulting in dermal vascular necrosis.