$\alpha$-maltose consists of

• A
  one $\alpha$-$D$-glucopyranose unit and one $\beta$-$D$-glucopyranose unit with $1-2$ glycosidic linkage
• B
  two $\alpha$-$D$-glucopyranose units with $1-2$ glycosidic linkage
• C
  two $\beta$-$D$-glucopyranose units with $1-4$ glycosidic linkage
• D
  two $\alpha$-$D$-glucopyranose units with $1-4$ glycosidic linkage