AIIMS 2018 Botany Nitrogen Metabolism MCQ Question

Option C represents free-living nitrogen-fixing bacteria, such as Azotobacter and Clostridium, which can convert atmospheric nitrogen (N₂) into ammonia (NH₃) independently of a host plant. These bacteria play a crucial role in the nitrogen cycle by enriching soil fertility. Other options may refer to symbiotic nitrogen-fixing bacteria, like Rhizobium, which require a host plant for nitrogen fixation, thus distinguishing them from the free-living types. Understanding the difference between these groups highlights the various ecological roles of nitrogen-fixing bacteria in ecosystems.