This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins and Minerals, Subject name: Biochemistry
Vitamin K dependent clotting factors are: 
Select and explain. 
A. Factor III & XI, B. Factor IX & X, C. Factor V & VIII, D. Factor XI & XIII
B: Factor IX & X
Answer: B: Factor IX & X 
Explanation: Vitamin K is the cofactor for g-carboxylation of glutamate residues of the proteins to produce g carboxy glutamate (gla)- Clotting factors contain 4 to 6 g-carboxyglutamate residues Eg- II VII IX X Protein C Protein S Protein Z Osteocalcin Transthyretin (Prealbumin)