Which one of the following super oxide is most stable

MO2(super oxides) are paramagnetic with one unpaired electron in pi anti bonding molecular orbital;MO2(super oxides) are yellow (or) orange in colour Lithium forms monoxidesSodium with limited oxygen forms monoxide and with excess oxygen forms peroxide;K, Rb and Cs form super oxides. Stability of super oxides increases with increase in cation size. This fact is explained by Lattice enthalpy effects.