Chlorine is allowed to react with an excess of ammonia. In this reaction,$1$ mole of chlorine can oxidize '$Z$' moles of $NH_3$. The value of '$Z$' is:

• A
  $\frac{3}{8}$
• B
  $\frac{8}{3}$
• C
  $\frac{2}{3}$
• D
  $\frac{3}{2}$