The two structures of D-glucopyranose forms are:

Anomers

The correct answer is option 1. anomers.

Anomers are stereoisomers of cyclic forms of sugars that differ in the configuration at the anomeric carbon, which is the carbon that bears the aldehyde or ketone functional group in the sugar's open-chain form.

In the case of D-glucopyranose, there are two possible anomers: \(\alpha\)-D-glucopyranose and \(\beta\)-D-glucopyranose. The only difference between these two anomers is the configuration of the hydroxyl group on carbon-1. In \(\alpha\)-D-glucopyranose, the hydroxyl group is on the same side of the ring as the aldehyde group. In \(\beta\)-D-glucopyranose, the hydroxyl group is on the opposite side of the ring as the aldehyde group.

The other options are incorrect. Option (1) enantiomers, are stereoisomers that are mirror images of each other. Option (2) epimers, are stereoisomers that differ in the configuration at a single chiral center. Option (4) geometrical isomers, are stereoisomers that differ in the arrangement of substituents around a double bond.