In the manufacture of $NH_3$ in Haber's continuous flow process involving the reaction $N_{2(g)} + 3H_{2(g)} \longleftrightarrow 2NH_{3(g)}$,$\Delta H = -22.08 \ kcal$. The favourable conditions are:

• A
  High pressure and low temperature due to low activation energy $(E_a).$
• B
  Low pressure and low temperature due to low $E_a$.
• C
  High pressure and elevated optimum temperature due to high $E_a$.
• D
  None of these.