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
[{'content': 'The 40 nm gap in between the tropocollagen molecule in collagen which serve as the site of bone formation is occupied by which of the following- \nSelect and explain. \nA. Carbohydrate, B. Ligand moiety, C. Calcium, D. All', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Calcium40 nm gap between the typrocollagen molecues serve as nucleation site for deposition of hydroxyapatite I ca5(p04)3(19H),1 with some phosphate] crystals in boneQ.', 'role': 'assistant'}]