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