Plesiosaur and Pliosaur were

Options

A. Flying reptiles
B. Herbivorous dinosaurs
C. Marine reptiles
D. Carnivorous dinosaurs.

Answer

**Step-by-Step Solution:**

1. **Identify the Organisms**: The question asks about Plesiosaur and Pliosaur. Both of these are types of reptiles that lived during the Mesozoic era.

2. **Determine Their Classification**: To classify Plesiosaur and Pliosaur, we need to consider their characteristics and the era they lived in. They are not flying reptiles, nor are they classified as dinosaurs.

3. **Examine Their Characteristics**:
- **Plesiosaur**: Characterized by a long neck, tapered body, blunt flippers, and a small head with sharp teeth. These features suggest adaptations for a marine environment.
- **Pliosaur**: Distinguished by a massive head, short neck, and streamlined body, also equipped with flippers for swimming.

4. **Establish Their Habitat**: Both Plesiosaur and Pliosaur were predominantly marine reptiles, meaning they lived in the ocean.

5. **Consider the Options**: The options provided are:
- Flying reptiles
- Herbivorous dinosaurs
- Marine reptiles
- Carnivorous dinosaurs

6. **Select the Correct Option**: Based on the characteristics and habitat of Plesiosaur and Pliosaur, the correct classification is "marine reptiles."

**Final Answer**: Plesiosaur and Pliosaur were **marine reptiles**.

---