What is the state of hybridisation of carbon in (a) $C{O}_{3}^{2-}$ (b) diamond (c) graphite?

The state of hybridisation of carbon in:
(a) $C{O}_{3}^{2-}$ C in $C{O}_{3}^{2-}$is $s{p}^{2}$ hybridised and is bonded to three oxygen atoms.
(b) Diamond Each carbon in diamond is $s{p}^{3}$ hybridised and is bound to four other carbon atoms.
(c) Graphite Each carbon atom in graphite is $s{p}^{2}$ hybridised and is bound to three other carbon atoms.