Q.α-D (+) Glucose and β-D (+) glucose are

Step 1. Recall from §14.1.3 that when glucose's open chain closes into its cyclic pyranose form, the originally achiral C1 (aldehyde) carbon becomes a new stereocentre, and the two resulting isomers -- differing only in the configuration at this one carbon -- are specifically called anomers, labelled α and β.

Step 2. Epimers (a) is the broader term for any two sugars differing at just one stereocentre, wherever that centre happens to be in the chain (e.g. glucose/galactose differ at C4); anomers are specifically epimers that differ at the anomeric carbon created by ring closure, so 'anomers' is the more precise and correct term here. Enantiomers (c) would require every stereocentre to be inverted (complete mirror images), which is not the case between α- and β-D …

Identify exactly where the two structures differ (only at the ring-closure carbon, C1) and match that to the specific vocabulary term for it -- anomers -- rather than the broa …

• Answering 'Epimers' (a) instead of the more specific 'Anomers' (b) -- anomers ARE a special case of epimers, but the question's own unit vocabulary reserves 'anomer' specifically for the pair created by ring …