Answer:
The correct option is B. bacteria
Step-by-step explanation:
Nitrogen-fixing bacteria can be described as bacteria which convert atmospheric nitrogen into a form which is usable for the plants. Without these bacteria, the process of recycling of nitrogen would not be possible. More than 90% of the nitrogen fixation is done by these microorganisms. Nitrogen fixation converts the nitrogen of the atmosphere into ammonia or other nitrogenous compounds which are usable by the plants. The nitrogen-fixing bacteria might have symbiotic relationships with plants.