The correct answer is B. nitrification.
Nitrification is the process by which ammonia is converted to nitrite and then nitrate. This process is carried out by nitrifying bacteria, which are chemoautotrophs that use ammonia as their energy source. Nitrifying bacteria are found in soil and water, and they play an important role in the nitrogen cycle.
Ammonification is the process by which organic nitrogen is converted to ammonia. This process is carried out by a variety of microorganisms, including bacteria, fungi, and protozoa. Ammonification is an important process in the nitrogen cycle, as it releases ammonia into the soil or water, where it can be used by plants or nitrifying bacteria.
Denitrification is the process by which nitrate is converted to nitrogen gas. This process is carried out by denitrifying bacteria, which are anaerobic bacteria that live in soil and water. Denitrification is an important process in the nitrogen cycle, as it removes nitrate from the soil or water, where it can pollute groundwater or cause eutrophication.
Therefore, the conversion of ammonia to nitrate is known as nitrification.