Answer:
PO4 3-
Step-by-step explanation:
A polyatomic ion is a group of atoms carrying a charge ( positive or negative ).
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zero.
Whereas S2- is not because it is an inorganic ion