Which of the following samples of reducing agents is /are chemically equivalent to 25mL of 0.2 N KMnO₄ to be reduced to Mn²⁺ and water?
A. 25 ml of 0.2MFeSO₄ to be oxidised to Fe³⁺
B. 50ml of 0.1MH₃AsO₃ to be oxidised to H₃AsO₄
C. 25 ml of 0.1MSO₃²⁻ to be oxidised to SO₄²⁻
D. 25 ml of 0.1MSnCl₂ to be oxidised to SnCl₄