From where does the nitrogen in the nitrogen cycle originate?

a. root nodules of legumes

b. the atmosphere

c. decomposers

d. nitrifying bacteria

The correct answer is B. The nitrogen in the nitrogen cycle originate from the atmosphere. It forms approximately 78% of the Earth's atmosphere. However, this form is not usable because it is in its most stable form therefore unreactive. This nitrogen gas needs to be converted into nitrate compound for it to be usable. Then, the nitrogen cycle starts.