Fructose reduces Fehling's solution due to the presence of:

Step-by-step solution

Fructose is a ketose sugar containing an -hydroxyketone group. Under the alkaline conditions of Fehling's solution, the -hydroxyketone group undergoes tautomerization (Lobry de Bruyn-van Ekenstein transformation) to form an enediol intermediate. This intermediate further converts into an aldose (glucose and mannose) which contains an aldehyde group. The newly formed aldehyde group then reduces Fehling's solution. Thus, the reducing property of fructose is due to the presence of the -hydroxyketone group. Answer: an