Which one is not a fish

Options

A. Cat fish
B. Dog fish
C. Silver fish
D. Lung Fish

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which of the given options is not classified as a fish.

2. **Reviewing the Options**: The options provided are:
- Catfish
- Dogfish
- Silverfish
- Lungfish

3. **Analyzing Each Option**:
- **Catfish**:
- Catfish belong to the superclass Pisces and specifically to the class Osteichthyes, which is the class of bony fishes. Therefore, catfish are indeed fish.

- **Dogfish**:
- Dogfish also belong to the superclass Pisces, but they are classified under Chondrichthyes, which are cartilaginous fishes. Thus, dogfish are also considered fish.

- **Silverfish**:
- Silverfish belong to the phylum Arthropoda and are classified under the class Insecta. Since they are insects and not part of the fish classification, silverfish are not fish.

- **Lungfish**:
- Lungfish belong to the superclass Pisces and are classified under Osteichthyes, making them bony fishes. Hence, lungfish are also fish.

4. **Conclusion**: After analyzing all the options, the only one that is not classified as a fish is **Silverfish**.

### Final Answer:
**Silverfish** is not a fish.

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