The number of sp2 hybrid orbitals on the carbon atom in co32– is

1

2

3

4

3

Explanation: Formula used for calculating the hybrid orbitals:

where, V = number of valence electrons present in central atom i.e. carbon = 4

N = number of monovalent atoms bonded to central atom=0

C = charge of cation = 0

A = charge of anion = -2

The number of electrons is 3 that means the hybridization will be and the electronic geometry of the molecule will be trigonal planar which will be formed by three hybrid orbitals.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)