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
You started a patient on oral warfarin. Which of the following factors show the most rapid decline in the blood levels after the initiation of warfarin therapy? 
Select and explain. 
A. Factor VII, B. Protein C, C. Factor X, D. Prothrombin
B: Protein C
Answer: B: Protein C 
Explanation: Protein C, protein S (both having anticoagulant property) and osteocalcin contain glutamate residues that require Vit. K dependent γ carboxylation. These are also inhibited by oral anticoagulants, but density of adult bone is not affected, though new bone formation may be depressed.
Reference: Essentials of Medical Pharmacology Seventh Edition KD TRIPATHI  page no 621