Statement I: D-glucose and D-manose are epimers

Statement II: They differ in configuration around only a second carbon atom

Both Statement I and Statement II are correct and Statement II is the correct explanation of Statement I

The correct answer is option 1. Both Statement I and Statement II are correct and Statement II is the correct explanation of Statement I.

Statement I: D-glucose and D-mannose are epimers.

This statement is correct. Epimers are stereoisomers that differ in the configuration of only one chiral center. D-glucose and D-mannose are both hexoses, which means that they have six carbon atoms. The only difference between the two molecules is the configuration of the hydroxyl group at the second carbon atom. In D-glucose, the hydroxyl group is on the right-hand side, while in D-mannose, the hydroxyl group is on the left-hand side.

Statement II: They differ in configuration around only second carbon atom.

This statement is also correct. As mentioned above, the only difference between D-glucose and D-mannose is the configuration of the hydroxyl group at the second carbon atom.

Since Statement II is the correct explanation of Statement I, the correct answer is Both Statement I and Statement II are correct and Statement II is the correct explanation of Statement I.