For the reaction $N_2 (g) + O_2(g) \leftrightharpoons 2NO (g)$, the equilibrium constant is $K_1$. The equilibrium constant is $K_2$ for the reaction $2NO(g) + O_2(g) \rightleftharpoons 2NO_2 (g).$ <br> What is $K$ for the reaction $NO_2 (g) \rightleftharpoons 1/2 N_2 (g) + O_2 (g)$ ?

Question

( A ) $[1/K_1K_2]^{1/2}$
( B ) $1 / (2 K_1 K_2)$
( C ) $1 / (4 K_1 K_2)$
( D ) $1/(K_1 K_2)$