Which one is not a platyhelminthes?

Options

A. Tapeworm
B. Liver fluke
C. Planaria
D. Hookworm

Answer

To determine which organism is not a member of the phylum Platyhelminthes (flatworms), we will analyze the given options one by one.

### Step-by-Step Solution:

1. **Understand the Phylum Platyhelminthes**:
- Platyhelminthes, commonly known as flatworms, are characterized by their soft, unsegmented bodies. They include various types of worms such as tapeworms, liver flukes, and planarians.

2. **Examine the Options**:
- **Option 1: Tapeworm**:
- Tapeworms belong to the phylum Platyhelminthes. Therefore, this option is incorrect as it is indeed a platyhelminth.

- **Option 2: Liver Fluke**:
- Liver flukes are also part of the Platyhelminthes phylum. Thus, this option is also incorrect as it is a platyhelminth.

- **Option 3: Planaria**:
- Planaria are flatworms and are included in the phylum Platyhelminthes. Hence, this option is incorrect as well.

- **Option 4: Hookworm**:
- Hookworms do not belong to the phylum Platyhelminthes; they are part of the phylum Nematoda (roundworms). Therefore, this option is correct as it is not a platyhelminth.

3. **Conclusion**:
- The organism that is not a platyhelminth is **Option 4: Hookworm**.

### Final Answer:
**Option 4: Hookworm** is not a platyhelminth.