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: Biochemistry
The oxidation of retinol produces:- 
Select and explain. 
A. Retinine, B. Beta-carotene, C. Retinal, D. Retinoic acid
C: Retinal
Answer: C: Retinal 
Explanation: Retinal (vitamin A aldehyde): 
This is an aldehyde form obtained by the oxidation of retinol. 
Retinal and retinol are interconvertible.
Key Concept:
Oxidation of retinol produces retinal
Oxidation of retinal produces retinoic acid.
Ref : Textbook of Biochemistry, Satyanarayana