Answer:
c.ammonium ... nitrites is the correct answer.
Explanation:
Nitrifying bacteria convert ammonium to nitrites and this process is called Nitrification.
Nitrification is a naturally occurring process by a specialized type of bacteria(nitrifying bacteria)
Nitrifying bacteria are Nitrosococcus, Nitrococcus, Nitrosomonas, and Nitrobacter.
The conversion of ammonium to nitrites is done by Nitrosomononas bacteria and it a complex process that needs oxygen, protein, and enzymes such as ammonia monooxygenase, hydroxylamine oxidoreductase.
