Nitrosomonas and Nitrobacter convert
A
Carbon dioxide to carbohydrates
B
Ammonium ion into nitrate
C
Nitrate ion into nitrogen molecule
Correct option is B. Ammonium ion into nitrate
Nitrification is a process of conversion of ammonium ions to nitrites and nitrites to nitrates. The bacteria that carry out this process are called as nitrifying bacteria. Nitrosomonas, Nitrosospira, Nitrosococcus convert ammonia into nitrites. Nitrobacter, Nitrospina, Nitrococcus convert nitrites into nitrates.
Thus, the correct answer is 'Ammonium ion into nitrate.'