On the basis of the +I effect of alkyl groups (and absence of any stabilising hyperconjugation for the negative centre), the correct order of stability of the carbanions is

1. A$(\mathrm{CH}{}_3){}_2\mathrm{CH}{}^{-}>(\mathrm{CH}{}_3){}_3\mathrm{C}{}^{-}>\mathrm{CH}{}_3{}^{-}>\mathrm{CH}{}_3\mathrm{CH}{}_2{}^{-}$
2. B$\mathrm{CH}{}_3{}^{-}>\mathrm{CH}{}_3\mathrm{CH}{}_2{}^{-}>(\mathrm{CH}{}_3){}_2\mathrm{CH}{}^{-}>(\mathrm{CH}{}_3){}_3\mathrm{C}{}^{-}$
3. C$(\mathrm{CH}{}_3){}_3\mathrm{C}{}^{-}>(\mathrm{CH}{}_3){}_2\mathrm{CH}{}^{-}>\mathrm{CH}{}_3\mathrm{CH}{}_2{}^{-}>\mathrm{CH}{}_3{}^{-}$
4. D$\mathrm{CH}{}_3\mathrm{CH}{}_2{}^{-}>\mathrm{CH}{}_3{}^{-}>(\mathrm{CH}{}_3){}_2\mathrm{CH}{}^{-}>(\mathrm{CH}{}_3){}_3\mathrm{C}{}^{-}$