Rhizobium of alfalfa group is

Answer: Option D

Rhizobium of alfalfa group is Melilolti.
The soil bacterium Sinorhizobium meliloti is capable of entering into a nitrogen-fixing symbiosis with Medicago sativa (alfalfa).
Alfalfa is a widely cultivated forage crop of substantial economic value that possesses excellent agricultural traits, in that its roots can fix atmospheric nitrogen molecules with the help of symbiotic rhizobia.
Particular low-molecular-weight forms of certain polysaccharides produced by S. meliloti are crucial for establishing this symbiosis.