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
Vitamin A activity is inhibited by 
Select and explain. 
A. Linetin, B. Black berries, C. Citral, D. Red cabbage
C: Citral
Answer: C: Citral 
Explanation: These results suggest that citral inhibits both the natural vitamin A in the plasma and the added synthetic vitamin A, thus producing changes in the tracheal epithelium characteristic of vitamin A deficiency.
Ref : The Effects of Vitamin A and Citral on Epithelial Differentiation in vitro, J. Embryol. exp. Morph., Vol. 11, Part 1, pp. 279-291