The correct option is A It is sp3 hybridised.
Characteristics of carbanion :
1. sp3 hybridized, geometry- tetrahedral, shape- pyramidal
2. Formed by heterolytic cleavage, when an electropositive element is attached to carbon atom.
3. Electron rich species (since carbon has 8 electrons in its valence shell)
4. The lone pair of electron resides in an sp3 hybridised orbital.
Hence option (a) is correct.