One of the following is not a fish

Options

A. Sucker fish
B. Flat fish
C. Flying fish
D. Cuttle fish

Answer

To determine which of the following options is not a fish, we will analyze each option one by one:

1. **Sucker Fish**:
- The sucker fish, commonly known as Hypostomus or Plecostomus, is a type of fish that is known for its bottom-feeding habits.
- **Conclusion**: This is a fish.

2. **Clam Fish**:
- The term "clam fish" typically refers to a type of fish that is found at the bottom of the sea. It is a ray-finned fish.
- **Conclusion**: This is also a fish.

3. **Flying Fish**:
- The flying fish, known scientifically as Exocetus, is famous for its ability to glide above the water surface.
- **Conclusion**: This is a fish as well.

4. **Cuttlefish**:
- Cuttlefish are marine animals that belong to the phylum Mollusca and are classified as cephalopods.
- **Conclusion**: This is not a fish.

After analyzing all the options, the correct answer is **Cuttlefish**, as it is not a fish but a marine animal belonging to a different phylum.