This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
Which of the following is a primer acting as an acceptor of glucose residues in glycogenesis? 
Select and explain. 
A. Carbohydrate, B. Lipid, C. Protein, D. Nucleic acid
C: Protein
Answer: C: Protein 
Explanation: Primer for Glycogen biosynthesis: Glycogenin protein-contains tyrosine to which Glucose chain attached.