Which of the following organisms cannot fix nitrogen? A. Azotobacter, B. Oscillatoria, C. Anabaena, D. Volvox, E. Nostoc. Choose…

Question

Which of the following organisms cannot fix nitrogen? A. Azotobacter, B. Oscillatoria, C. Anabaena, D. Volvox, E. Nostoc.

Choose the correct answer from the options given below:

1. A. A only
2. B. D only (Correct answer)
3. C. B only
4. D. E only

Correct Answer

Option B — D only

Detailed Solution & Explanation

The correct answer is D only (Volvox).

Key Points

• *Azotobacter* (a free-living aerobic bacterium) and the cyanobacteria *Oscillatoria*, *Anabaena* and *Nostoc* are all nitrogen fixers.
• Volvox is a colonial green alga and cannot fix nitrogen.