Character found only in mammals :-

Options

A. Homeothermy
B. Viviparity
C. Dicondylic skull
D. Diaphragm

Answer

To answer the question regarding the character found only in mammals, we will analyze the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a characteristic that is unique to mammals. This means we need to identify a feature that is not found in any other class of animals.

2. **Evaluating Homeothermy**:
- The first option is homeothermy, which refers to the ability to maintain a constant internal body temperature.
- **Analysis**: Both mammals and birds are homeothermic. Therefore, this characteristic is not exclusive to mammals.
- **Conclusion**: This option is incorrect.

3. **Evaluating Live Birth**:
- The second option refers to giving birth to live young (viviparity).
- **Analysis**: While most mammals give birth to live young, some reptiles and fish also exhibit this trait. Thus, this characteristic is not unique to mammals.
- **Conclusion**: This option is incorrect.

4. **Evaluating Dichotylidic Skull**:
- The third option mentions the dichotylidic skull.
- **Analysis**: This type of skull is also present in some amphibians, so it is not exclusive to mammals.
- **Conclusion**: This option is incorrect.

5. **Evaluating Diaphragm**:
- The fourth option is the diaphragm.
- **Analysis**: The diaphragm is a muscular structure that separates the thoracic cavity from the abdominal cavity and is crucial for respiration in mammals. No other animal group possesses a diaphragm as a primary respiratory muscle.
- **Conclusion**: This option is correct as it is a unique characteristic of mammals.

### Final Answer:
The character found only in mammals is the **diaphragm**.

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