The correct option is A PO3−4,C2O2−4
According to Bronsted lowry: Acid is any species that can donate a proton and a base is any species that can accept a proton.
Acid−H+⇌Conjugate base
In the given reaction,
PO3−4 is accepting a proton to form HPO2−4, hence it is bronsted base.
C2O2−4 is accepting a proton to form HC2O−4, hence it is bronsted base.