Adding powdered $\mathrm{Pb}$ and $\mathrm{Fe}$ to a solution containing $1 \mathrm{M}$ each of ${\mathrm{Pb}}^{2+}$ and ${\mathrm{Fe}}^{2+}$ ions would result in the formation of $-({\mathrm{E}}_{{\mathrm{Pb}}^{2+}/\mathrm{Pb}}^0=-0.126 \mathrm{V}$ and $\left.{\mathrm{E}}_{{\mathrm{Fe}}^{2+}/\mathrm{Fe}}^0=-0.44 \mathrm{V}\right)$

Which is the strongest oxidising agent among the species given below?

$\left(\mathrm{i}\right) {\ln }^{3+} \mathrm{E}°=-1.34 \mathrm{V}$
$\left(\mathrm{ii}\right) {\mathrm{Au}}^{3+} \mathrm{E}°=1.40 \mathrm{V}$
$\left(\mathrm{iii}\right) {\mathrm{Hg}}^{2+} {\mathrm{E}}^{\mathrm{o}}=0.867 \mathrm{V}$
$\left(\mathrm{iv}\right) {\mathrm{Cr}}^{3+} \mathrm{E}°=-0.786 \mathrm{V}$

Which of the following aqueous solution has the lowest electrical conductance?