Question SPM.1A.HL.TZ0.28

What is the equilibrium constant expression for the following reaction?

2SO₃(g)$\rightleftharpoons$2SO₂(g) + O₂(g)

A.  $\frac{2{\left[{\mathrm{SO}}_2\right]}^2\left[{\mathrm{O}}_2\right]}{{\left[{\mathrm{SO}}_3\right]}^2}$

B.  $\frac{{\left[{\mathrm{SO}}_2\right]}^2+\left[{\mathrm{O}}_2\right]}{{\left[{\mathrm{SO}}_3\right]}^2 }$

C.  $\frac{{\left[{\mathrm{SO}}_3\right]}^2}{{\left[{\mathrm{SO}}_2\right]}^2\left[{\mathrm{O}}_2\right]}$

D.  $\frac{2\left[{\mathrm{SO}}_2\right]\left[{\mathrm{O}}_2\right]}{2\left[{\mathrm{SO}}_3\right]}$