In an element (X) shows two oxidation states $+2$ and $+3$ and forms an oxide in such a way the ratio of the element showing $+2$ and $+2$ states is $1:3$ in compound the formulae of

Question

$ (a)\;X_4O_{11} \\(b)\; X_8O_{11} \\ (c)\;X_{5}O_{11} \\ (d)\;A_9 O_{11}$