If the sewage is fully oxidized, the nitrogen is in the form of A. Nitrites B. Ammonia C. Nitramines D. Nitrates

The correct answer is D. Nitrates.

Nitrification is the process

by which ammonia is converted into nitrites and then into nitrates. This process is carried out by bacteria in the presence of oxygen. Nitrates are the most oxidized form of nitrogen and are the end product of nitrification. They are relatively stable and are not easily converted back into ammonia.

Ammonia is the simplest form of nitrogen and is the most reduced form. It is highly reactive and can be toxic to plants and animals. Nitrites are intermediate forms of nitrogen and are less toxic than ammonia. However, they can also be toxic to plants and animals in high concentrations.

Nitrates are the most oxidized form of nitrogen and are the end product of nitrification. They are relatively stable and are not easily converted back into ammonia. Nitrates are essential for plant growth and are used by plants to produce proteins and other organic compounds.

In conclusion, the correct answer is D. Nitrates.