Final answer:
The oxyanion among the given ions is d) PO4³−, which is known as the phosphate ion.
Step-by-step explanation:
The ion that is an oxyanion is d) PO43−. An oxyanion is a polyatomic ion that is composed of a central atom bonded to one or more oxygen atoms. The central atom is typically a nonmetal or a metalloid. In the case of PO43−, phosphorus (P) is the central atom and it is bonded to four oxygen atoms, forming the phosphate ion, which is an oxyanion. Oxyanions are commonly found in various types of salts and can participate in ionic bonding with cations. The ion PO₄³⁻ is an oxyanion because it consists of a phosphorus atom bonded to four oxygen atoms.