Many bacteria possess hairy appendages on their cell walls. They are

Options

A. Hairs
B. Flagella
C. Cilia
D. Fimbriae.

Answer

To solve the question about the hairy appendages present on the cell walls of many bacteria, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structures**: The question mentions "hairy appendages" on the cell walls of bacteria. We need to consider what these structures could be.

2. **Evaluate the Options**: The options provided are hairs, flagella, cilia, and fimbri. We will analyze each option to determine which one fits the description of "hairy appendages".

3. **Analyze Hairs**: Hairs are structures typically found in mammals and are not present in bacteria. Since bacteria belong to the kingdom Monera and are prokaryotic, we can eliminate this option.

4. **Analyze Flagella**: Flagella are long, whip-like structures used for movement in bacteria. While they are present in some bacteria, they do not fit the description of "hairy appendages" as they are larger and primarily serve a different function (locomotion). Thus, we can eliminate this option as well.

5. **Analyze Cilia**: Cilia are small, hair-like structures found in certain eukaryotic organisms, particularly unicellular protists like paramecium. They are also used for locomotion but are not found in bacteria. Therefore, we can eliminate this option too.

6. **Analyze Fimbri**: Fimbri (or fimbriae) are small, hair-like projections that are numerous and present on the cell walls of bacteria. They play a crucial role in helping bacteria attach to surfaces, including host tissues. This aligns perfectly with the description of "hairy appendages".

7. **Conclusion**: Based on the analysis, the correct answer is **fimbri** (option 4), as they are the structures that match the description given in the question.

### Final Answer:
The hairy appendages on the cell walls of many bacteria are **fimbri**.

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