JEE Main 2017 · 9 Apr · Shift 1, Chemistry question 48

$\ce{Ti^2+}$, $\ce{V^2+}$ and $\ce{Cr^2+}$ are strong reducing agents and are oxidised by $\ce{H+}$, releasing hydrogen. $\ce{Mn^2+}$ ($d^5$) is stable, since $E^\circ(\ce{Mn^3+/Mn^2+})=+1.57$ V, so it does not.