Nitrogen in the atmosphere must be "fixed" before it can be used by plants. atmospheric nitrogen is "fixed" by

nitrogen fixing bacteria

Explanation:

Nitrogen in the forms of nitrates, nitrites and ammonia are essential for the growth of the plants. Nitrogen present in the atmosphere is fixed in the soil by the nitrogen fixing bacteria. As plants cannot absorb nitrogen from the air. The bacteria convert atmospheric nitrogen into inorganic forms such as nitrates, nitrites and ammonia which are directly absorbed by the plants by their roots.

i dont know it at allnow im just getting points at this pint

im not intirely sure but i think the anwser is d relative humidity