I don't know how to approach this question

Iron (II) sulfate is oxidized - it means iron changes from +2 to +3
If iron is oxidized then dichromate is reduced from Cr₂O₇ ^2- in which its oxidation number is +6 to lower oxidation number.
a and b clearly out because chromium is not undergoing any change, C is also out because Fe has same +2 oxidation number.
d and e can be the option now we need some more information about Fe₂(SO₄)₃ compound. If you check the solubility list rule no 3 - all sulfates are soluble except with 6 metals -CaSO₄,BaSO₄ ,SrSO₄ Ag₂SO₄,PbSO₄ and HgSO₄.
Fe₂(SO₄)₃ is a strong electrolyte so completely soluble. So the compound can not come out as solid and it should be in solution as Fe³⁺ and SO₄^2-
Based on this understanding e is the right answer.