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: Social & Preventive Medicine
Which pathway describes the synthesis of metabolically active vitamin D: March 2004 
Select and explain. 
A. Liver - skin - kidney, B. Gut - kidney - liver, C. Kidney - liver - skin, D. Skin - liver - kidney
D: Skin - liver - kidney
Answer: D: Skin - liver - kidney 
Explanation: Ans. D i.e. Skin - liver - kidney