Each of the given pairs below has two different compounds with one element in common. Identify the pair which has the indicated element in the same oxidation state in both compounds.

• A. Oxygen in H₂O and H₂O₂
• B. Iron in FeCl₂ and FeSO₄
• C. Sulfur in SO₂ and Na₂S₂O₃
• D. Chlorine in KCl and HOCl

Answer: (B)