Why vinyl carbanion is more stable than methyl carbanion

The stability order of the above carbocations is 

Which of the following carbocations is most stable?

The major products $\mathrm{A}$ and $\mathrm{B}$ in the following reactions are

Choose the correct statement regarding the formation of carbocations A and B given :-

The stability of carbanions

follows the order

 Arrange the following free radicals in order of decreasing stability:

$\mathrm{Methyl}\left(\mathrm{I}\right), \mathrm{Vinyl}\left(\mathrm{II}\right),\mathrm{Allyl}\left(\mathrm{III}\right) \mathrm{and} \mathrm{benzyl}\left(\mathrm{IV}\right)$

The correct order of stability of given carbocation is:

Arrange the following carbocations in decreasing order of stability.

Which of the following is most stable$?$

Arrange the following carbanions in order of their decreasing stability

(i) ${\mathrm{H}}_3\mathrm{C}-\mathrm{C}\equiv {\mathrm{C}}^{-}$

(ii) $\mathrm{H}-\mathrm{C}\equiv {\mathrm{C}}^{-}$

(iii) ${\mathrm{H}}_3\mathrm{C}-{\mathrm{CH}}_2^{-}$