What statement most directly demonstrates a way that the geosphere is involved in the nitrogen cycle

The statement that most directly explain this concept is "nitrifying bacteria that convert ammonia into nitrites and nitrates are found in the soil".

Explanation:

Bacteria living in the soil in root nodules of various plants are directly involved in the nitrogen cycle. The nitrifying bacteria "Nitrobacters" and "Nitrosomonas" can fix atmospheric nitrogen and can convert it into nitrates and nitrites. As plants can not directly fix that atmospheric nitrogen so these Nitrobacters and Nitrosomonas who lives in symbiotic relation in their root nodules do this nitrogen fixation for them. So these bacteria provide them nitrates and nitrates that plants can directly uptake and can use in their essential metabolic cycles. In this way, Geosphere plays a critical role in nitrogen fixation.