In the chemical reaction $N_2 + 3H_2 \rightleftharpoons 2NH_3$ at equilibrium point,state whether:

• A
  Equal volumes of $N_2$ and $H_2$ are reacting
• B
  Equal masses of $N_2$ and $H_2$ are reacting
• C
  The reaction has stopped
• D
  The same amount of ammonia is formed as is decomposed into $N_2$ and $H_2$