Principle of Le Chatelier

Which of the following statements is NOT correct about the following endothermic reaction which is in equilibrium: $\text{SO}_{3}(g)\rightleftharpoons \text{SO}_{2}(g) + \frac{1}{2} \text{O}_{2}(g)?$

(A) The reaction moves to the left when O $_{2}$ (g) is added.
(B) The reaction moves to the left when the mixture is compressed at a constant temperature.
(C) The reaction moves to the left when the mixture is cooled.
(D) The equilibrium is maintained when an inert gas is inserted with pressure/temperature constant.