Which gas-phase reaction has $K_p$ equal to $K_c$ at the same temperature?

• A. $2SO{2}_{}\left(g\right)+O_2\left(g\right)\rightleftharpoons 2SO{3}_{}\left(g\right)$
• B. $N_{2}O\left(g\right)\rightleftharpoons N_2\left(g\right)+\frac{1}{2}{O}_2\left(g\right)$
• C. $N_2\left(g\right)+3H_2\left(g\right)\rightleftharpoons 2N_{\mathrm{H}}{3}_{}\left(g\right)$
• D. $H_2\left(g\right)+I_2\left(g\right)\rightleftharpoons 2HI\left(g\right)$

Answer: (D)