Correct Option (a)
Reason : The enzyme nitrogenase is required for the process of biological nitrogen fixation only. Fixation of atmospheric nitrogen occur through other route also. Neither nitrification (conversion of ammonium to nitrate) nor conversion of nitrate to nitrite require nitrogenase.
Correct Option (a) Reason : The enzyme nitrogenase is required for the process of biological nitrogen fixation only. Fixation of atmospheric nitrogen occur through other route also. Neither nitrification (conversion of ammonium to nitrate) nor conversion of nitrate to nitrite require nitrogenase.