b
The reaction of aqueous \(K M n O_{4}\) with \(H_{2} O_{2}\) in acidic medium is \(3 H_{2} S O_{4}+2 K M n O_{4}+5 H_{2} O_{2} \rightarrow\)

\(5 \mathrm{O}_{2}+2 \mathrm{Mn} \mathrm{SO}_{4}+8 \mathrm{H}_{2} \mathrm{O}+\mathrm{K}_{2} \mathrm{SO}_{4}\)

In the above reaction, \(K M n O_{4}\) oxidises \(H_{2} O_{2}\) to \(O_{2}\) and itself \(\left[M n O_{4}^{-}\right]\) gets reduced to \(M n^{2+}\) ion as \(M n S O_{4}\) 

Hence, aqueous solution of \(K M n O_{4} .\) with \(H_{2} O_{2}\) yields \(M n^{2+}\) and \(O_{2}\) in acidic conditions.