<prompt> The major storage and circulatory form of vitamin D is:-25-hydroxycholecalciferol1,25-dihydroxycholecalciferolCholecalciferolCalcitriol  <response>: Cholecalciferol is first hydroxylated at 25th position to 25-hydroxycholecalciferol 25-OH o3 bv a specific hydroxylase present in liver. 25-OH D3 is the major storage and circulatory form of vitamin D.Reference: Satyanarayana- Biochemistry, 3rd edition, pg-125 