What is maltose?
Maltose is a disaccharide made of two D-glucose units joined by an $\alpha(1\rightarrow 4)$ glycosidic bond.

Meaning of "anomer of maltose"
In maltose, one glucose unit uses its anomeric carbon in the glycosidic bond, while the other glucose unit has a free anomeric carbon.
Therefore, maltose can exist as $\alpha$- and $\beta$-anomers, depending on the configuration at the free anomeric carbon.

Condition for the $\alpha$-anomer of maltose
For D-glucose in Haworth form:

• $\alpha$ means the OH at the free anomeric carbon is down.
• The glycosidic linkage in maltose is already $\alpha(1\rightarrow 4)$, i.e. the first glucose contributes its anomeric carbon in the $\alpha$-orientation.

So the correct structure of $\alpha$-maltose must satisfy:

• two glucose rings,
• linkage is $\alpha(1\rightarrow 4)$,
• free anomeric OH on the second glucose is $\alpha$ (down).

Matching with the given options
Among the standard structures, this corresponds to Option C.

Conclusion
The correct structure of the $\alpha$-anomer of maltose is C.