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 body

Explanation

To determine the common characteristic shared by birds and mammals, we will analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Understanding the Options**: The options given are:
- A) Pigmented skin
- B) Pneumatic bones
- C) Viviparity
- D) Warm-blooded body

2. **Analyzing Option A: Pigmented Skin**:
- Pigmented skin is primarily an adaptive feature found in mammals. It provides coloration and protection against UV radiation.
- Birds do not have pigmented skin in the same way mammals do; instead, they have feathers which can be pigmented.
- **Conclusion**: This characteristic is not shared by both birds and mammals.

3. **Analyzing Option B: Pneumatic Bones**:
- Pneumatic bones are hollow bones that are lighter and are specifically adapted for flight in birds.
- Mammals do not possess pneumatic bones; this feature is unique to birds.
- **Conclusion**: This characteristic is not shared by both birds and mammals.

4. **Analyzing Option C: Viviparity**:
- Viviparity refers to giving birth to live young. This is a characteristic of most mammals.
- Birds, on the other hand, are oviparous, meaning they lay eggs.
- **Conclusion**: This characteristic is not shared by both birds and mammals.

5. **Analyzing Option D: Warm-blooded Body**:
- Warm-blooded, or endothermic, animals can maintain a constant body temperature regardless of their environment.
- Both birds and mammals are warm-blooded, which allows them to thrive in various environments.
- **Conclusion**: This characteristic is shared by both birds and mammals.

6. **Final Answer**:
- After analyzing all the options, the common characteristic shared by birds and mammals is **D) Warm-blooded body**.