What is mutarotation

Question

$\begin{array}{1 1} \text{(a) Mutarotation is the change in specific rotation of a chiral compound due to epimerization.} \\ \text{(b)Mutarotation is the change in specific rotation of a achiral compound due to epimerization.} \\ \text{(c) Mutarotation refers to the change in otical rotation over time due to a change between isomers.} \\ \text{(d) None of the above}\end{array}$