Consider the following exothermic reaction
2SO_2(g) + O_2(g) ↔ 2SO_3(g)
If the temperature of the reaction from 800°C to 500°C, and no other change takes place, then

• A.the reaction rate increases
• B.concentration of SO₃ decreases
• C.concentration of SO₃ increases
• D.O₃ gas becomes unreactive