Roundworms differ from flatworms in having of:-

Options

A. Dorsal nerve cord
B. Flame cells
C. Circulatory system
D. Pseudocoelom

Answer

To answer the question "Roundworms differ from flatworms in having of:", we need to analyze the characteristics of both groups of worms.

### Step-by-Step Solution:

1. **Identify the Groups**:
- Roundworms belong to the phylum Nematoda.
- Flatworms belong to the phylum Platyhelminthes.

2. **Examine the Options**:
- **Dorsal Nerve Coat**: This is present in both roundworms and flatworms. Therefore, this option is incorrect.
- **Flame Cells**: These specialized excretory cells are found in flatworms and not in roundworms. Thus, this option is also incorrect.
- **Circulatory System**: Both roundworms and flatworms lack a true circulatory system. Hence, this option is incorrect as well.
- **Pseudocoelomate**: Roundworms are classified as pseudocoelomates, which means they have a body cavity that is not completely lined by mesoderm. In contrast, flatworms are acoelomates, meaning they do not have a body cavity at all. This option is correct.

3. **Conclusion**:
- The correct answer is that roundworms differ from flatworms in having a pseudocoelomate structure.

### Final Answer:
Roundworms differ from flatworms in having a pseudocoelomate body structure.

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