balance the following equation and classify what type of reaction it is: S₈ + O₂ → SO₃

a) 2S₈ + 7O₂ → 2SO₃
b) S₈ + 8O₂ → 8SO₃
c) 2S₈ + 3O₂ → 2SO₃
d) S₈ + 5O₂ → 8SO₃