Nitrogen fixation involves the enzyme ____ catalyzing the reaction:
N₂ + 10 ____ + ____ e− → 2 NH₄⁺ + H₂

A) nitrate reductase; H₂O; 6
B) nitrogenase; H⁺; 8
C) nitrogenase; H⁺; 2
D) nitrogen reductase; H₂O; 6
E) none are true