The order of decreasing stability of the
carbanions :

1. (CH₃)₃C–
2. (CH₃)₂ CH-    $$\begin{gathered} 3.C{H}_{3}C{H}_2^{-} \\ 4. C_6{H}_{5}C{H}_2^{-} \end{gathered}$$
   
    

Given data: It is given to identify that the order of decreasing stability of the
carbanions.

Explanation: The stability of carbanions is less when +I is less

Stability  of carbanions is 1⁰ > 2⁰ > 3⁰

Because of resonance stablization Benzyl carbanion is stable.

The larger the number of alkyl groups on a carbanion, the more stable it becomes. Phenyl groups are not as effective as alkyl groups in stabilizing the carbanion because there is no resonance energy involved. The stability of the carbanion increases with an increasing atomic weight of the central atom (C in this case).

Hence, option( B) IV> III > II> I is correct answer.