Which of the following is a free living nitrogen fixing bacteria ? (A) Pseudomonas (B) Azotobacter (C) Rhizobium (D) Nitrosomonas
Which of the following is a free living nitrogen fixing bacteria ? (A) Pseudomonas (B) Azotobacter (C) Rhizobium (D) Nitrosomonas

Answer: (B) Azotobacter

Explanation: Azotobacter is a genus of bacteria that are huge, free-living, Gram negative, obiigately aerobic, rod-shaped bacteria that can fix nitrogen non-symbiotically.