All Eubacteria have-

Options

A. Cell wall
B. Flagella
C. Heterocyst
D. All the above

Answer

To answer the question "All Eubacteria have-", we need to analyze the options provided:

1. **Cell Wall**: Eubacteria, also known as true bacteria, are characterized by having a cell wall. This is a fundamental feature of their structure, as it provides shape and protection.

2. **Flagella**: Some Eubacteria are motile, and they possess flagella, which are tail-like structures that help in movement. However, not all Eubacteria have flagella; only those that are motile do.

3. **Heterocysts**: Heterocysts are specialized cells found in certain cyanobacteria (a group of Eubacteria), such as Nostoc and Anabaena. They are not present in all Eubacteria, only in specific types.

4. **All of the Above**: This option suggests that all the previous features are present in all Eubacteria, which is incorrect because not all Eubacteria possess flagella or heterocysts.

Based on this analysis, the correct answer to the question "All Eubacteria have-" is:

**Cell Wall**.

### Step-by-Step Solution:
1. **Identify the characteristics of Eubacteria**: Understand that Eubacteria are also known as true bacteria and have specific features.
2. **Evaluate the options**:
- **Cell Wall**: Confirm that all Eubacteria have a cell wall.
- **Flagella**: Recognize that flagella are present only in motile Eubacteria, not all.
- **Heterocysts**: Understand that heterocysts are specific to certain cyanobacteria, not all Eubacteria.
3. **Conclude**: Since only the cell wall is a universal characteristic of all Eubacteria, the answer is that all Eubacteria have a cell wall.