Which of the following is a symbiotic nitrogen fixing bacterium?

Rhizobium is a symbiotic nitrogen-fixing bacterium. It forms a mutualistic relationship with leguminous plants such as peas, beans, and clover. Rhizobium resides in the root nodules of these plants and converts atmospheric nitrogen into ammonia, a form of nitrogen that plants can use for growth. This process is known as biological nitrogen fixation and is crucial for soil fertility and the productivity of crops. The relationship between Rhizobium and leguminous plants is beneficial for both parties: the bacterium gets carbohydrates from the plant, while the plant receives a natural source of nitrogen. This natural fertilization process is important for sustainable agriculture and reducing the need for chemical fertilizers.