Which of the following carbohydrates is the C-2 epimer of D-glucose?

Step-by-step solution

Epimers are diastereomers that differ in the configuration of only one stereogenic center. D-glucose and D-mannose differ in their stereochemistry only at the C-2 position. In D-glucose, the -OH group at C-2 is on the right side in the Fischer projection, whereas in D-mannose, the -OH group at C-2 is on the left side. Therefore, D-mannose is the C-2 epimer of D-glucose. D-galactose is the C-4 epimer of D-glucose, L-glucose is the enantiomer of D-glucose, and D-fructose is a functional isomer (a ketose) of D-glucose