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': 'Vitamin D \nSelect and explain. \nA. Absorption requires bile pigments, B. Synthesis is regulated at the reaction catalyzed by 15-hydroxylase, C. Deficiency on adults leads to rickets, D. Along with PTH, increases calcium resorption from bone', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]