The most stable carbanion among the following is

Select the correct option for stability of following carbanions :

$\begin{array}{c}\stackrel{\ominus }{\mathrm{C}}{\mathrm{H}}_3\\ \left(\mathrm{I}\right)\end{array}$;  $\begin{array}{c}{\mathrm{C}}_6{\mathrm{H}}_5^{\ominus }{\mathrm{CH}}_2\\ \left(\mathrm{II}\right)\end{array}$;   $\begin{array}{c}{\mathrm{CH}}_3-\underset{\stackrel{|}{{\mathrm{CH}}_3}}{\overset{\underset{|}{{\mathrm{CH}}_3}}{{\mathrm{C}}^{\ominus }}}\\ \left(\mathrm{III}\right)\end{array}$