With regard to the bilogical nitrogen fixation by Rhizobium in association with soy bean, which one of the following statement/statements does not hold true?A. Nitrogcnase may require oxygen for its functioningB. Nitrogenase is Mo - Fe proteinC. Leg-hemoglobin is a pink coloured pig- mentD. Nitrogenase helps to convert `N_2` gas into two molecules of ammonia