Annelids with definite number of segments belongs to the class

Options

A. Hirudinea
B. oligocheata
C. polychaeta
D. archiannelida

Answer

**Step-by-Step Solution:**

1. **Understanding Annelids**: Annelids are segmented worms that belong to the phylum Annelida. They are characterized by their segmented bodies.

2. **Identifying Classes of Annelids**: Annelids are divided into three main classes:
- Class Hirudinea (leeches)
- Class Oligochaeta (earthworms)
- Class Polychaeta (marine worms)

3. **Defining Segmentation**: The question specifically asks for Annelids with a definite number of segments. This means we are looking for a class where the number of segments is constant and can be easily counted.

4. **Analyzing Each Class**:
- **Class Hirudinea**: Leeches have a definite number of segments, typically 34, which is constant across individuals.
- **Class Oligochaeta**: Earthworms have numerous segments, but the number can vary significantly among different species, making it difficult to count.
- **Class Polychaeta**: These worms also have numerous segments, and their segmentation is more pronounced, but again, the number of segments can vary widely.
- **Class Archiannelida**: This class includes primitive annelids with less pronounced segmentation, making it unsuitable for our criteria.

5. **Conclusion**: Based on the analysis, the class of Annelids with a definite number of segments is **Class Hirudinea**.

**Final Answer**: Class Hirudinea

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