Cyanobacteria/Blue green algae are-

Options

A. Unicellular only
B. Colonlal only
C. Filamentous only
D. Unicellular, Colonial or filamentous

Answer

**Step-by-Step Solution:**

1. **Understanding Cyanobacteria**: Cyanobacteria, commonly known as blue-green algae, are a group of photosynthetic bacteria. They are often found in various aquatic environments.

2. **Cell Structure**: Cyanobacteria can exist in different forms. They can be unicellular, meaning they consist of a single cell.

3. **Colonial Forms**: In addition to being unicellular, some cyanobacteria can form colonies. This means that multiple cells are grouped together, functioning as a single unit.

4. **Filamentous Forms**: Some cyanobacteria can also be filamentous. This means they can form long chains or filaments of cells that are connected together.

5. **Conclusion**: Given that cyanobacteria can exist as unicellular, colonial, and filamentous forms, the correct answer to the question is that they can be all three: unicellular, colonial, and filamentous.

**Final Answer**: D) Unicellular, colonial, and filamentous.

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