Which of the following is a correct representation of the reaction rate for the reaction stated below?
$N_{2(g)} + 3H_{2(g)} \rightleftharpoons 2NH_{3(g)}$

• A
  $-\frac{d[N_2]}{dt} = -\frac{1}{3} \frac{d[H_2]}{dt} = \frac{1}{2} \frac{d[NH_3]}{dt}$
• B
  $-\frac{d[N_2]}{dt} = -\frac{1}{3} \frac{d[H_2]}{dt} = -\frac{1}{2} \frac{d[NH_3]}{dt}$
• C
  $-\frac{d[N_2]}{dt} = \frac{1}{3} \frac{d[H_2]}{dt} = \frac{1}{2} \frac{d[NH_3]}{dt}$
• D
  $\frac{d[N_2]}{dt} = \frac{1}{3} \frac{d[H_2]}{dt} = \frac{1}{2} \frac{d[NH_3]}{dt}$