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: Biochemistry
Which amino acid residues gets carboxylated by vitamin K during post translational modification 
Select and explain. 
A. Aspartate, B. Glutamate, C. Oxaloacetate, D. Lysine
B: Glutamate
Answer: B: Glutamate 
Explanation: Vitamin K is required for the post translational gamma carboxylation of glutamic acid residues of clotting factors.