Question

describing the nitrogen cyc
how do plants obtain nitrogen?
they remove it from the air.
they absorb it through their roots.
they fix it in their leaves.
they produce it in their stems.

Explanation:

Plants cannot directly use atmospheric nitrogen. Nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia. Then, through nitrification, ammonia is converted into nitrates. Plants absorb these nitrates (a form of nitrogen) through their roots.

Answer:

They absorb it through their roots.