Biology

The correct answer is A.nitrogen fixation.

Nitrogen fixation is the process of converting nitrogen gas (N₂) from the atmosphere into usable compounds, typically ammonia (NH₃) or ammonium (NH₄⁺), which can be taken up by plants. This process is carried out by nitrogen-fixing bacteria, either in the soil or in the roots of certain plants (like legumes), and can also occur through natural processes like lightning.

Here's a breakdown of the other terms to explain why they are not correct:

B.Nitrogen composition: This is not a recognized process in the nitrogen cycle. The term is not used in the context of nitrogen cycling or ...