Correct Answer:
Option A
Explanation:
Nitrogen fixation means converting the atmospheric nitrogen to Ammonia or to other compounds which can be readily used by other organisms. As stated in the question, the nitrogen available in the atmosphere is inert, so it must be converted into a form so that the organisms can use it. The bacteria responsible for this activity are known as Nitrogen Fixing Bacteria and are an important element of the ecosystem. Some of these Nitrogen fixing bacteria live freely in the soil while some are associated with the crops. Some examples of Nitrogen fixing bacteria are Rhizobium and Azospirillum.
