Which of the Following Is the Correct Balanced Equation for the Equilibrium

Which of the following is the correct balanced equation for the equilibrium expression given below?
$K _ { p } = \frac { P _ { \mathrm { SO } _ { 3 } } ^ { 2 } } { P _ { \mathrm { O } _ { 2 } } P _ { \mathrm { SO } _ { 2 } } ^ { 2 } }$

A) 2 SO₂(g) + O₂(g) $\rightleftharpoons$ 2 SO₃(g)
B) 2 SO₃(g) $\rightleftharpoons$ 2 SO₂(g) + O₂(g)
C) 2 SO₃(aq) $\rightleftharpoons$ 2 SO₂(aq) + O₂(aq)
D) 2 SO₂(aq) + O₂(aq) $\rightleftharpoons$ 2 SO₃(aq)
E) SO₂(g) + $\frac { 1 } { 2 }$ O₂(g) $\rightleftharpoons$ SO₃(g)