# Which of the following species are planar?

$\begin{array}{1 1}(a)\;\text{Singlet carbene}\\(b)\;\text{Nitromethyl carbanion}\\(c)\;\text{Both (a) & (b)}\\(d)\;\text{Isopropyl carbanion}\end{array}$

In singlet carbene C-atom is $SP^2$ hybridized state.Carbonium ion carbon is in $SP^2$ hybridized state.Carbanion carbon is in $SP^2$ hybridized state if it is linked to $SP^2$ hybridized atom because of resonance.
Hence (c) is the correct answer.