AP EAMCET Engineering 2016 Code C Paper

Consider the following statements
I) CS+ ion is more highly hydrated than other alkali metal ions
II) Among the alkali metals, only lithium forms a stable nitride by direct combination with nitrogen
III) Among alkali metal Li, Na, K, Rb, the metal, Rb has the highest melting point
IV) Among alkali metals Li, Na, K, Rb only Li forms peroxide when heated with oxygen