In the following groups : $I\; - OAc ; \;\; II \; -OMe ; \; III \;-OSO_2 Me\; ; (IV) \; -OSO_2 CF_3$ the order of leaving groups ability is

Question

$ (a)\;I > II > III >IV \\ (b)\;IV > III > I >II \\ (c)\;III > II > I >IV \\ (d)\;II > III > IV >I $