Although 78% of earth's atmosphere is nitrogen, nitrogen is limited in most ecosystems because

Because the natural conversion of atmospheric nitrogen occurs via only lightning and nitrogen-fixing bacteria.

Explanation:

Nitrogen, which means “saltpeter former” or “what forms nitrates”. It is one of the most abundant elements in the universe. On Earth it is mostly gaseous, filling up to 78% of atmospheric air volume. However, despite its abundance, this element is limited to living things in most ecosystems. This is because most living things are unable to absorb nitrogen in its gaseous form and need a convention of atmospheric nitrogen in an assimilable form. The natural conversion of atmospheric nitrogen occurs only through nitrogen-fixing bacteria, these bacteria are called Rizobium.

answer; i believe that the correct answer is (b) melosis; plz check first.good luck

but there is no

i guess you forgot putting it.