Some characters are given below. Which of them are true for the cyanobacteria?
a) Oxygenic photosynthesis b) Non-oxygenic chemotrophism
c) Oxygenic chemotrophism
d) Ability of `N_(2)` fixation.

Options

A. a and b
B. a and c
C. a and d
D. b and d

Answer

To determine which characters are true for cyanobacteria, let's analyze each option step by step:

1. **Oxygenic Photosynthesis (Option a)**:
- Cyanobacteria are known for performing oxygenic photosynthesis. This means they use sunlight to convert carbon dioxide and water into glucose and oxygen. The presence of chlorophyll allows them to capture light energy, leading to the release of oxygen as a byproduct.
- **Conclusion**: This statement is true.

2. **Non-oxygenic Chemotrophism (Option b)**:
- Chemotrophism refers to the process of obtaining energy through the oxidation of inorganic or organic compounds. Non-oxygenic chemotrophism implies that an organism derives energy without producing oxygen. However, cyanobacteria primarily rely on sunlight for energy through photosynthesis, not through chemotrophic processes.
- **Conclusion**: This statement is false.

3. **Oxygenic Chemotrophism (Option c)**:
- Oxygenic chemotrophism would suggest that cyanobacteria obtain energy through the oxidation of compounds while producing oxygen. However, cyanobacteria do not obtain energy through chemotrophic means; they perform photosynthesis. Therefore, this option is also incorrect.
- **Conclusion**: This statement is false.

4. **Ability of N₂ Fixation (Option d)**:
- Cyanobacteria possess specialized cells called heterocysts that allow them to fix atmospheric nitrogen (N₂) into a form that can be utilized by plants. This ability is crucial for the nitrogen cycle and supports plant growth, especially in symbiotic relationships with leguminous plants.
- **Conclusion**: This statement is true.

### Final Answer:
The true statements regarding cyanobacteria are:
- a) Oxygenic photosynthesis
- d) Ability of N₂ fixation