The formation of peroxide linkage in either due to the exposure in air can be detected by treating in with

Question

$\begin{array}{1 1}(a)\;Na\\(b)\;dil\;HCl\\(c)\;\text{Aqueous ferrous ammonium sulphate followed by addition of ammonium thiocyanate}\\(d)\;dil.NaOH\end{array}$