The most unique mammalian characteristic is the:-

Options

A. Mammary glands
B. Internal fertilisation
C. Warm blooded body
D. Heart is four chambered

Answer

To solve the question regarding the most unique mammalian characteristic, we can follow these steps:

1. **Understand the Question**: The question asks for the most unique characteristic that defines mammals.

2. **Analyze the Options**:
- **Option A: Mammary glands** - These are glands that produce milk in female mammals.
- **Option B: Internal fertilization** - This is a reproductive process where fertilization occurs inside the female's body.
- **Option C: Warm-blooded body** - This refers to the ability to maintain a constant body temperature regardless of the environment.
- **Option D: Heart is four-chambered** - This refers to the structure of the heart, which is divided into four chambers.

3. **Evaluate Each Option**:
- **Mammary glands** are exclusive to mammals and are essential for the nourishment of their young.
- **Internal fertilization** is also found in other animal groups, not just mammals.
- **Warm-bloodedness** (endothermy) is a characteristic of birds as well.
- **Four-chambered heart** is a feature of birds and some reptiles too.

4. **Identify the Most Unique Characteristic**: Among the options, mammary glands are the most distinctive feature that sets mammals apart from other animal groups.

5. **Conclusion**: The most unique mammalian characteristic is the presence of mammary glands.

**Final Answer**: A) Mammary glands

---