In multistage equilibrium conversion of SO₂ to SO₃ (2SO₂ + O₂ ↔ 2SO₃), the reverse reaction becomes appreciable at a temperature of 550° C. The percentage equilibrium conversion of SO₂ to SO₃ can be increased by

• A. increasing the oxygen concentration.
• B. putting more quantity of V₂O₅ catalyst in the converter.
• C. removing some quantity of SO₃ during intermediate stage.
• D. maintaining low temperature & pressure in the converter.