Which of the following reactions shows nitrogen fixation?

• A
  $2 NH_{4}^{+} + 2 O_{2} + 8 e^{-} \rightarrow N_{2} + 4 H_{2}O$
• B
  $2 NH_{3} \rightarrow N_{2} + 3 H_{2}$
• C
  $N_{2} + 8 H^{+} + 8 e^{-} + 16 ATP \rightarrow 2 NH_{3} + H_{2} + 16 ADP + 16 \Pi$
• D
  $2 N_{2} + \text{Glucose} \rightarrow 2 \text{Amino acids}$