Ascaris is characterized by the

Options

A. presence of neither true coelom nor metamerism
B. presence of true coelom but absence of metamerism
C. presence of true coelom and metamerism (metamerisation)
D. absence of true coelom by presence

Answer

### Step-by-Step Solution:

1. **Identify the Organism**: Ascaris is a genus of parasitic nematodes, commonly known as roundworms. It belongs to the phylum Nematoda.

2. **Understand the Characteristics**:
- **Coelom**: Ascaris does not possess a true coelom. Instead, it has a pseudocoelom, which is a body cavity that is not completely lined by mesoderm.
- **Metamerism**: Ascaris exhibits no metamerism, meaning its body is not segmented. This is a characteristic feature of nematodes.

3. **Phylum Classification**: Ascaris is classified under the phylum Aschelminthes (or Nematoda), which is known for organisms that lack true coeloms and segmentation.

4. **Disease Association**: Ascaris is known to cause a disease called Ascariasis, which primarily affects children who may ingest eggs present in contaminated soil.

5. **Final Conclusion**: Based on the characteristics of Ascaris, it is characterized by the absence of a true coelom and the absence of metamerism.

### Answer:
Ascaris is characterized by the absence of a true coelom and the absence of metamerism.

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