This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy of skin, Subject name: Dental
Most abundant aminoacid in collagen is 
Select and explain. 
A. Proline, B. Lysine, C. Threonine, D. Glycine
D: Glycine
Answer: D: Glycine 
Explanation: COLLAGEN Collagens are triple helices formed by amino acid chains where every third residue is glycine (Gly-X-Y), with a high likelihood of proline and hydroxyproline/ hydroxylysine in the X and Y positions, respectively. Ref:- Review of Dermatology by Alikhan; pg num:-7