Question

Are (a) D-glucitol, (b) D-galactitol, and (c) D-glycerol optically active?

Short answer

D-glycerol is optically active. Hence, the correct answer is option (c).

Step-by-step solution

Introduction of optically active substance.

Optically active substances are such compounds which have chiral center and thus show optical rotation when observed through polarimeter.

D-glucitol and D-galactitol are optically inactive.

D-glucitol and D-galactitol are optically inactive due to absence of chiral center.

Therefore, the options (a) and (b) are incorrect.