Acidified solution of K2Cr2O7 oxidises which of the following?

Cr₂O₇^2- + 3SO₃^2- + 8H⁺ → 2Cr³⁺ + 3SO₄^2- + 4H₂O

K₂Cr₂O₇ can oxidise SO₃^2- (Sulphite ions) to SO₄^2- (Sulphate ions)

Nitrate ion, ferric ion, and borate ions are already in their highest oxidation state thus they cannot be further oxidized.