Which of the following statements is/are incorrect ?
(i) Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial habitats.
(ii) Anabaena, Nostoc and Oscillatoria are photosynthetic `N_(2)`-fixing cyanobacteria.
(iii) Tolypothrix (BGA) can increase rice production by about `20%`
(iv) BGA add organic matter to the soil and increase its fertility.
(v) In our country, biofertilisers are not available commercially in the markets for farmers.

Options

A. (v) only
B. (iv) only
C. (iii) only
D. None of these

Explanation

To determine which statements are incorrect, let's analyze each statement one by one:

1. **Statement (i)**: "Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial habitats."
- **Analysis**: This statement is correct. Cyanobacteria are indeed autotrophic organisms, meaning they can produce their own food through photosynthesis. They are found in a variety of environments, including both aquatic and terrestrial habitats.

2. **Statement (ii)**: "Anabaena, Nostoc and Oscillatoria are photosynthetic N₂-fixing cyanobacteria."
- **Analysis**: This statement is also correct. Anabaena, Nostoc, and Oscillatoria are well-known genera of cyanobacteria that can perform photosynthesis and fix atmospheric nitrogen, making them important for nitrogen cycling in ecosystems.

3. **Statement (iii)**: "Tolypothrix (BGA) can increase rice production by about 20%."
- **Analysis**: This statement is correct. Tolypothrix is a type of blue-green algae (BGA) that has been shown to enhance rice production by fixing nitrogen and improving soil fertility.

4. **Statement (iv)**: "BGA add organic matter to the soil and increase its fertility."
- **Analysis**: This statement is correct. Blue-green algae contribute organic matter to the soil through their growth and decay, which enhances soil fertility by providing nutrients.

5. **Statement (v)**: "In our country, biofertilisers are not available commercially in the markets for farmers."
- **Analysis**: This statement is incorrect. Biofertilisers, including those derived from cyanobacteria and other microorganisms, are available commercially in many markets for farmers in various countries, including India.

**Conclusion**: The incorrect statement is (v) only.

### Final Answer:
The incorrect statement is: (v) In our country, biofertilisers are not available commercially in the markets for farmers.

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