Which Statement Describes the Relationship Between Ammonia Oxidizers and Nitrite

Multiple Choice

Which statement describes the relationship between ammonia oxidizers and nitrite oxidizers?

A) Ammonium oxidizers use ammonium as an energy source, oxidizing it to nitrite. The nitrite produced then serves as the energy source for nitrite oxidizers.
B) Ammonium oxidizers use ammonium as an energy source, oxidizing it to nitrate. The nitrate produced then serves as the energy source for nitrite oxidizers.
C) Ammonium oxidizers use urea as an energy source, oxidizing it to nitrite. The nitrite produced then serves as the carbon source for nitrite oxidizers.
D) Ammonium oxidizers use ammonium as an energy source, reducing it to nitrate. The nitrate produced then serves as the energy source for nitrite oxidizers.
E) None of these explains the relationship-ammonia and nitrite are produced by different nutrient cycles which also involve sulfur reduction.