The term anomers of glucose refers to

Isomers of glucose that differ in configuration at carbon one (C-1)

The answer is (4) isomers of glucose that differ in configuration at carbon one (C-1).

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

In the case of glucose, the anomeric carbon is carbon-1. The two anomers of glucose are alpha-glucose and beta-glucose. The only difference between the two anomers is the configuration of the hydroxyl group on carbon-1. In alpha-glucose, the hydroxyl group is on the same side of the ring as the aldehyde group. In beta-glucose, the hydroxyl group is on the opposite side of the ring as the aldehyde group.

The other options are incorrect. Option (1) is incorrect because anomers differ in configuration at carbon-1, not carbons one and four. Option (2) is incorrect because anomers are not mixtures of enantiomers. Option (3) is incorrect because anomers are not enantiomers.