Dinosaurs are

Options

A. extinct amphibians
B. Extinct reptiles
C. Primitive mammals
D. Living reptiles

Answer

**Step-by-Step Solution:**

1. **Understanding Dinosaurs**: Dinosaurs are a group of reptiles that existed millions of years ago. They are characterized by their large body size and diverse forms.

2. **Timeline of Existence**: Dinosaurs first appeared around 245 million years ago during the Triassic period. This is crucial to understanding their historical context.

3. **Duration of Existence**: Dinosaurs thrived for approximately 180 million years before most of them became extinct during the Cretaceous period.

4. **Classification**: Dinosaurs are classified as reptiles. This is an important distinction because it helps eliminate other options provided in the question.

5. **Evaluating Options**:
- **Extinct Amphibians**: This is incorrect because dinosaurs are not amphibians.
- **Extinct Reptiles**: This is correct as dinosaurs are indeed a group of reptiles that are now extinct.
- **Primitive Mammals**: This is incorrect since dinosaurs do not share characteristics with mammals.
- **Living Reptiles**: This is incorrect because dinosaurs are not living today; they are extinct.

6. **Conclusion**: The correct answer is that dinosaurs are "extinct reptiles."

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