Answer:
a) Representation - (in attachment)
b) Tetrahedral geometry and
c) 
hybrid orbitals invovle sigma bonding.
orbitals are formed by the overlapping of d-orbitals of sulfur with p-orbitals of oxygen.
Explanation:
a)
Representation in attachment.
The overall charge in the both structures are -2. The structure (b) is favored by the resonance structures since the formal charge with in the species are remained.
Therefore, structure (b) is the better representation of sulfate ion.
b)
In sulfate ion, sulfur atom is attached with four different oxygen atoms. According to the VSEPR theory , the sufate ion has tetrahedral geometry.
There is four sigma bonds and zero lone pairs present on the central metal atom.
Hence, the hybridization of the sulfur atom is
c)
The s and p orbitals of sulfur invovles hybridization and form sigma bonds.The orbitals of sulfur involves bonding.
Therefore, bonds are formed by the overlapping of d-orbitals of sulfur with p-orbitals of oxygen.
