Lactose is made of

• A

  $\alpha$-D-glucose only
• B

  $\alpha$-D-glucose and $\beta$-D-glucose
• C

  $\alpha$-D-galactose and $\beta$-D-glucose
• Correct answer
  D

  $\beta$-D-galactose and $\beta$-D-glucose

Solution

Lactose (milk sugar) is a disaccharide, obtained by the condensation of one molecule of $\beta$-D-galactopyranose and one molecule of $\beta$-D-glucopyranose.

Hence, the correct answer is option: 'D'.