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 major storage and circulatory form of vitamin D is:- \nSelect and explain. \nA. 25-hydroxycholecalciferol, B. 1,25-dihydroxycholecalciferol, C. Cholecalciferol, D. Calcitriol', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Cholecalciferol is first hydroxylated at\xa025th position to\xa025-hydroxycholecalciferol (25-OH o3) bv\xa0a\xa0specific hydroxylase present in\xa0 liver. 25-OH\xa0D3 is the major storage and circulatory form of vitamin D.\nReference: Satyanarayana- Biochemistry, 3rd edition, pg-125', 'role': 'assistant'}]