The correct option is B Rhizobium, Azotobacter, Nostoc
Rhizobium, Azotobacter, Nostoc are nitrogen fixing bacteria.
Nitrosomonas - Nitrifying bacteria
Streptococcus - Cause infections
Lactobacillus - Lactic acid bacteria
Nitrobacter - Nitrifying bacteria
Streptobacillus - Cause infections
Clostridium - Cause infections