Ascaris is a parasitic :

Options

A. roundworm
B. flatworm
C. tapeworm
D. sponge

Explanation

**Step-by-Step Solution:**

1. **Identify the Organism**: The question asks about Ascaris, which is known to be a parasitic organism.

2. **Understand the Classification**: Ascaris is classified under the phylum Nematoda. This phylum is known for roundworms.

3. **Evaluate the Options**:
- **Option 1: Roundworm** - This is correct, as Ascaris is indeed a roundworm.
- **Option 2: Flatworm** - This is incorrect; flatworms belong to a different phylum (Platyhelminthes).
- **Option 3: Tapeworm** - This is also incorrect; tapeworms are a type of flatworm and belong to the phylum Platyhelminthes.
- **Option 4: Sponge** - This is incorrect; sponges belong to the phylum Porifera.

4. **Conclusion**: Since Ascaris is a roundworm and belongs to the phylum Nematoda, the correct answer is that Ascaris is a parasitic roundworm.

**Final Answer**: Ascaris is a parasitic roundworm.

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