Answer
c. Fe2(SO4)3
Step-by-step explanation
The polyatomic ion (SO₄)⁻² has a net charge of -2 and iron (III) ion, Fe⁺³ has an oxidation number of +3. For a compound to be formed between them, two of Fe⁺³ will need three of the polyatomic ion, (SO₄)⁻² and the formula of the compound will be Fe2(SO4)3.