A vitamin that functions both as a hormone and a visual pigmen?
A. Riboflavin B. Folic acid C. Thiamine D. Retinol/ Retinal Solution: D Retinol acts as a vitamin hormone as well as a visual pigment. The scientific name of vitamin A is retinol. Night blindness is caused by deficiency of vitamin A. Vitamin A exists in three oxidation states: Retinal, Retinol and Retinoic Acid (Retin A). Hence, (d) is the correct answer.