Answer:
A. a five-membered cyclic hemiacetal.
Explanation:
Fructose is a hexose sugar with a ketone group unlike glucose which has an aldehyde group.
The fructose also forms a cyclic structure due to formation of hemiacetal bond however unlike glucose the cyclic structure formed is a five membered ring.
The hemiacetal bond is formed when an alcohol reacts with a carbonyl group.
The structure of fructose is shown in the figure.
