The halogen $($Group $17$ elements$)$:

The correct option is C show variable oxidation state of $-1,+1,+3,+5$ and $+7$ in their various compounds
Fluorine is the most electronegative in halogen family so it has oxidation number of -1 in all its compounds but Cl,Br and I are less electronegative so these elements prepare compounds with oxidation number of +1,+3,+5 and +7.