What happens to iodine when iodate ions, ${\text{IO}}_3^ -$, are converted to iodine molecules, ${{\text{I}}_{\text{2}}}$?

A.     It undergoes reduction and its oxidation number changes from $- 1$ to 0

B.     It undergoes oxidation and its oxidation number changes from $- 1$ to 0

C.     It undergoes reduction and its oxidation number changes from $+ 5$ to 0

D.     It undergoes oxidation and its oxidation number changes from $+ 5$ to 0

C