Answer: Option (d) is the correct answer.
Explanation:
A polyatomic ion is defined as the ion formed by two or more number of atoms which actually covalently combine together.
This means that only non-metals combine covalently together as a covalent bond is formed by sharing of electrons.
For example, S and O atoms are covalent and they tend to form polyatomic ions when combine together.
Whereas K and F, Li and I, Mg and Br are all metals and non-metals. So, they will always form an ionic bond as the metal will transfer its valence electrons to the non-metal.
Thus, we can conclude that out of the given options S and O pairs of elements is most likely to be part of a polyatomic ion.
