If the HCOO^- Ion Is Described Using Delocalized Electrons,why Can

If the HCOO^- ion is described using delocalized electrons,why can the oxygen atoms not have sp³ hybrids?

A) There must be an unhybridized p orbital to form the pi bond system.
B) The s orbital must be unhybridized to form the pi bond system.
C) There is no hybridization in systems with delocalized electrons.
D) Molecular orbital theory does not include hybridization.
E) The four lobes repel each other too strongly.