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

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

The perioxide linkage can be detected by treating the sample with terrous ammonium sulphate followed by the addition of ammonium thiocynate.Ferrous ions is oxidized to terric ions which produces red coloration with $NH_4CNS$.
Hence (c) is the correct answer.