Question:

Find incorrect statements
A. Rhodospirillum is aerobic  
B. Anabaena and Nostoc are free-living nitrogen fixers  
C. Azotobacter is anaerobic  
D. Beijerinckia is aerobic  

Show Hint

Remember that nitrogen-fixing bacteria like Azotobacter and Beijerinckia are aerobic, whereas Rhodospirillum can be anaerobic depending on the conditions.
Updated On: Mar 18, 2026
  • C, D
  • A, C
  • A, B
  • B, D
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The Correct Option is B

Solution and Explanation

Analysis of Statements:

A. Rhodospirillum is aerobic: āŒ Incorrect. šŸ”¹ Rhodospirillum is generally anaerobic under certain conditions and can perform anoxygenic photosynthesis.

B. Anabaena and Nostoc are free-living nitrogen fixers: āœ… Correct. šŸ”¹ Anabaena and Nostoc are cyanobacteria that fix atmospheric nitrogen and are free-living in aquatic or moist environments.

C. Azotobacter is anaerobic: āŒ Incorrect. šŸ”¹ Azotobacter is an aerobic, free-living nitrogen-fixing bacterium.

D. Beijerinckia is aerobic: āœ… Correct. šŸ”¹ Beijerinckia is an aerobic nitrogen-fixing bacterium.

Thus, the incorrect statements are: A and C

āœ… Correct Answer: (2) A, C.

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