Turbelllarians are

Options

A. free living nematodes
B. parastic nematodes
C. free living flatworms
D. parastic trematodes

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about Turbellarians. We need to identify what class or type they belong to within the phylum Platyhelminthes.

2. **Identifying the Phylum**: Turbellarians are part of the phylum Platyhelminthes. This phylum is known for flatworms, which includes various classes.

3. **Classifying Platyhelminthes**: The phylum Platyhelminthes is divided into three main classes:
- Cestoda (tapeworms)
- Trematoda (flukes)
- Turbellaria (free-living flatworms)

4. **Eliminating Incorrect Options**:
- The option "parasitic trematodes" can be ruled out because trematodes are a different class within the same phylum.
- The options "free-living nematodes" and "parasitic nematodes" can also be eliminated because nematodes belong to a different phylum (Nematoda) and are not flatworms.

5. **Identifying the Correct Option**: Since Turbellarians are classified as free-living flatworms within the phylum Platyhelminthes, the correct answer is "free-living flatworms."

### Final Answer:
Turbellarians are free-living flatworms.

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