Shown Here Are the Four Steps That Show How Sulfur $\rarr$

Shown here are the four steps that show how sulfur in coal is converted to sulfuric acid in acid rain. Which step, if any, shows an unbalanced equation

A) S(s) + O₂(g) $\rarr$ SO₂(g)
B) SO₂(g) + OH(g) $\rarr$ HOSO₂(g)
C) HOSO₂(g) + O₂ $\rarr$ HO₂(g) + SO₃(g)
D) SO₃(g) + H₂O(l) $\rarr$ H₂SO₄(aq)
E) None of the above are unbalanced equations