Answer:
B
Explanation:
The reason that B is the correct answer, is as follows:
1. There is nitrogen in the air, in the form of N₂. Animals and plants cannot assimilate nitrogen in this form, so it is converted to ammonia, nitrates and nitrites by bacteria.
2. Once it is in the form of nitrogen containing compounds, plants then absorb the compounds and can use the nitrogen in them to build amino acids and other essential structures.
3. Animals will consume plants, and that way obtain the nitrogen stored in the plants. Once they have eaten the plants, they then absorb the nitrogen to use it in the formation of our own proteins and amino acids.
4. When there is too much nitrogen in our body, it is excreted as ammonia or urine, once in that form, bacteria then convert the nitrogen containing compounds back into atmospheric nitrogen in the form of N₂.
