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: Pharmacology
Warfarin act by 
Select and explain. 
A. Inhibiting the activation of vitamin K dependent factors, B. Inhibiting thrombin indirectly through antithrombin III, C. Directly inhibiting thrombin, D. Inhibiting Gp IIb/IIIa
A: Inhibiting the activation of vitamin K dependent factors
Answer: A: Inhibiting the activation of vitamin K dependent factors 
Explanation: None