\(Fe ^{3+}\) 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 \(Pb ^{4+}\)
$A.$ $\mathrm{Mn}_2 \mathrm{O}_7$ ઓરડાના તાપમાને તૈલી છે.
$B.$ $\mathrm{V}_2 \mathrm{O}_4$ એસીડ સાથે પ્રક્રિયાથી $\mathrm{VO}_2^{2+}$ આપે છે.
$C.$ $\mathrm{CrO}$ બેજીક ઓક્સાઈડ છે.
$D.$ $\mathrm{V}_2 \mathrm{O}_5$ એસીડ સાથે પ્રક્રિયા કરે છે.