Fe is an important component of enzymes

Answer: Option D

Fe is an important component of all the given enzymes that are nitrogenase, nitrate reductase, and nitrite reductase. All these are enzymes responsible for nitrogen fixation.
Iron is an essential cofactor for a variety of redox reactions in plant metabolism and Fe requires enzymes to catalyze reactions that also involve oxygen, as a reagent or product of the reaction itself or as an entry or end point a metabolic pathway.