Identify the mammalian group in which mammary glands are without nipples :-

Options

A. Metatheria
B. Eutheria
C. prototheria
D. All of the above

Answer

To solve the question "Identify the mammalian group in which mammary glands are without nipples," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Classification of Mammals**:
- Mammals are classified into three main subclasses:
- **Prototheria**: Egg-laying mammals (monotremes).
- **Metatheria**: Marsupials (pouch mammals).
- **Eutheria**: Placental mammals.

2. **Identify Characteristics of Each Group**:
- **Prototheria**: These mammals lay eggs and do not have nipples. The young lap up milk from the mother's skin.
- **Metatheria**: These mammals have nipples and give birth to underdeveloped young that continue to develop in a pouch.
- **Eutheria**: These mammals also have nipples and give birth to more developed young.

3. **Focus on the Question**:
- The question specifically asks for the group where mammary glands are without nipples.

4. **Determine the Correct Group**:
- Since prototherians (monotremes) are the only group that lacks nipples, they are the correct answer.

5. **Conclusion**:
- Therefore, the mammalian group in which mammary glands are without nipples is **Prototheria**.

### Final Answer:
**Prototheria**

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