Round worms differ from flat worms in having_______.

Options

A. flame cells
B. pseudocoel
C. segmented body
D. flagella

Answer

**Step-by-Step Solution:**

1. **Identify the Types of Worms**:
- Round worms belong to the phylum **Aschelminthes**.
- Flat worms belong to the phylum **Platyhelminthes**.

2. **Understand Body Cavity Differences**:
- Round worms (Aschelminthes) possess a body cavity known as a **pseudocoelom**. This means they have a fluid-filled space between the body wall and the digestive tract.
- Flat worms (Platyhelminthes) do not have a true body cavity; they are **acoelomate**, meaning they lack a body cavity altogether.

3. **Conclusion**:
- The key difference between round worms and flat worms is that round worms have a **pseudocoelom**, while flat worms do not have any body cavity.

**Final Answer**: Round worms differ from flat worms in having a **pseudocoelom**.

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