The $\alpha$ - And $\beta$ -Pyranose Forms Of $D$ -Glucose Interconvert by
A) "Ring-Flipping" Between the Two Chair Conformations

The $\alpha$ - and $\beta$ -pyranose forms of $D$ -glucose interconvert by

A) "ring-flipping" between the two chair conformations.
B) ring-opening and ring-closing through the open-chain aldehyde form.
C) epimerization through the enol tautomer.
D) $\mathrm{S}_{\mathrm{N}} 2$ inversion with nucleophilic hydroxide ion.