This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Role of liver in vitamin D metabolism 
Select and explain. 
A. Catalyzes rate limiting steb, B. 1-hydroxylation, C. 25-hydroxylation, D. 24-hydroxylation
C: 25-hydroxylation
Answer: C: 25-hydroxylation 
Explanation: Found in the liver, this enzyme is a microsomal vitamin D hydroxylase that conves vitamin D into 25-hydroxyvitamin D (calcidiol), which is the major circulatory form of the vitamin.