Birds and mammals share one of the following characteristics as a common feature

Options

A. Pigmented skin
B. Pneumatic bones
C. Viviparity
D. Warm blooded

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks for a common characteristic shared by birds and mammals.

2. **Review the Options**: The options provided include:
- Pigmented skin
- Pneumatic bones
- Viviparity
- Warm-blooded (homeotherms)

3. **Analyze Each Option**:
- **Pigmented Skin**: Birds have various pigments in their skin and feathers, while mammals have a more limited range of pigments (primarily melanin). This characteristic is not shared.
- **Pneumatic Bones**: These are hollow bones found in birds to reduce weight for flight. Mammals do not have pneumatic bones, so this is not a shared feature.
- **Viviparity**: This refers to giving birth to live young, which is a characteristic of mammals. Birds lay eggs, so this is not a common feature.
- **Warm-blooded (Homeotherms)**: Both birds and mammals are warm-blooded, meaning they can regulate their body temperature internally regardless of the external environment.

4. **Conclusion**: The only common characteristic shared by birds and mammals is that they are both warm-blooded (homeotherms).

5. **Final Answer**: The correct answer is the fourth option: Warm-blooded.

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