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
In a warfarin treated patient skin necrosis is found in : a) Protein C deficiency b) Protein S deficiency c) AT III deficiency d) Factor VII deficiency e) Factor X deficiency 
Select and explain. 
A. bd, B. ad, C. ab, D. ac
C: ab
Answer: C: ab 
Explanation: None