.A nonphotosynthetic aerobic nitrogen fixing soil bacterium is (a) Rhizobium (b) Clostridium (c) Azotobacter (d) Klebsiella.
Option C A nonphotosynthetic aerobic nitrogen fixing soil bacterium is Azotobacter. Azotobacter is free living soil bacteria that are able to pick up dinitrogen from the soil and fixes it into organic nitrogenous material like amino acid.
