d
\(Ag\) has the electronic configuration \([ Kr ] \,4 d ^{10} \,5 s ^1\) Hence \(+1\) is a stable oxidation state for it.

\(Fe ^{3+}\) ion is more stable due to its half-filled \(3 d ^5\) electron configuration. As half filled and completely filled shells are more stable \(Fe ^{3+}\) ion is more stable than \(Fe ^{2+}\)

The \(Sn ^{2+}\) ions convert to \(Sn ^{4+}\) ions because the tin\((IV)\) oxidation state is more stable than tin\((II)\).

In non-transition elements of p-block, lower oxidation state is more stable due to inert pair effect e.g., \(Pb ^{2+}\) is more stable than \(Pb ^{4+}\)