This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins, Subject name: Biochemistry
Richest source of retinoids is? 
Select and explain. 
A. Cod liver oil, B. Halibut liver oil, C. Butter, D. Margarine
B: Halibut liver oil
Answer: B: Halibut liver oil 
Explanation: Ans. (b) Halibut liver oilRef: Harper's Biochemistry 27/e, chapter 44, Textbook of medical biochemistry S. Ramakrishnan 3/e, p 393