Which of the following class of animals is not a vertebrate?

Options

A. Fish
B. Reptiles
C. Birds
D. Insects

Answer

To determine which class of animals is not a vertebrate, we can follow these steps:

1. **Understand the Definition of Vertebrates**: Vertebrates are animals that possess a backbone or spinal column. This includes animals that have a vertebral column at some stage of their life cycle.

2. **Identify the Classes of Vertebrates**: The main classes of vertebrates include:
- Fishes
- Amphibians
- Reptiles
- Birds
- Mammals

3. **Examine the Options Provided**: The question typically provides a list of animal classes. We need to analyze each option to see if it falls under the category of vertebrates.

4. **Identify Invertebrates**: Invertebrates are animals that do not have a backbone. Common examples include insects, arachnids, and mollusks.

5. **Analyze the Options**: If the options include classes like fishes, reptiles, birds, amphibians, and mammals, they are all vertebrates. If there is an option like insects, that would be the class that is not a vertebrate.

6. **Conclusion**: Based on the analysis, the class of animals that is not a vertebrate is typically insects.

### Final Answer:
The class of animals that is not a vertebrate is **Insects**.