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: Medicine
Fish is a pure source of : 
Select and explain. 
A. Vitamin A, B. Proteins, C. Iron, D. Iodine
D: Iodine
Answer: D: Iodine 
Explanation: Fish is a pure source of Iodine and Carbohydrates.