What structural feature distinguishes D-glucose from D-fructose?

• A. D-glucose lacks chiral centers, unlike D-fructose.
• B. D-glucose has an additional hydroxyl group compared to D-fructose.
• C. D-glucose has an aldehyde group at the first carbon, while D-fructose has a ketone group at the second carbon.
• D. D-glucose has a longer carbon chain than D-fructose.

Answer: (C)