For the reaction $N_{2(g)} + O_{2(g)} \rightleftharpoons 2NO_{(g)}$,the equilibrium constant is $K_1$. For the reaction $2NO_{(g)} + O_{2(g)} \rightleftharpoons 2NO_{2(g)}$,the equilibrium constant is $K_2$. The equilibrium constant $K$ for the reaction $NO_{2(g)} \rightleftharpoons \frac{1}{2}N_{2(g)} + O_{2(g)}$ will be:

• A
  $\frac{1}{\sqrt{K_1 K_2}}$
• B
  $\frac{1}{2 K_1 K_2}$
• C
  $\frac{1}{4 K_1 K_2}$
• D
  $\left(\frac{1}{K_1 K_2}\right)^{1/2}$