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: Physiology
The site at which 1,25-hydroxylation of Vitamin-D takes place in the kidneys is: 
Select and explain. 
A. Collecting ducts, B. Glomerulus, C. Proximal convoluted tubules, D. Distal convoluted tubules
C: Proximal convoluted tubules
Answer: C: Proximal convoluted tubules 
Explanation: Proximal convoluted tubules