What is the Kc expression for this reaction?
2 NO(g) + O2(g) ⇌ 2 NO2(g)

a)Kc = [NO2]2 / [NO]2 [O2]
b)Kc = [NO]2 [O2] / [NO2]2
c)Kc = [NO]2 [O2] [NO2]2
d)Kc = [NO2]2 / [NO]2 + [O2]