Recall the composition of maltose

Maltose is a disaccharide formed by the condensation of two glucose units.

Nature of linkage in maltose

In maltose, the two glucose molecules are joined by an $\alpha(1\to 4)$ glycosidic bond.

This means the first glucose contributes its anomeric carbon in the $\alpha$-configuration to form the bond.

Identify the monomers

Therefore, maltose is made up of: $\alpha\text{-D-glucose} + \alpha\text{-D-glucose}$

Check the options

• A: $\alpha$-D-glucose and $\alpha$-D-galactose $\rightarrow$ This is not maltose.
• B: $\alpha$-D-glucose and $\alpha$-D-fructose $\rightarrow$ This corresponds to sucrose, not maltose.
• C: $\alpha$-D-glucose and $\alpha$-D-glucose $\rightarrow$ Correct.
• D: $\alpha$-D-glucose and $\beta$-D-glucose $\rightarrow$ Not the standard composition used to describe maltose in this context.

Final answer

The two monomers in maltose are: $\boxed{\alpha\text{-D-glucose and }\alpha\text{-D-glucose}}$