Amongst the following mammals which of the following is a monotreme?

Options

A. Macropus (Kangaroo)
B. Ornithorhynchus (Platypus)
C. Balaenoptera (Blue whale)
D. Elephas (Elephant)

Answer

To determine which of the given mammals is a monotreme, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Classification of Mammals**:
- Mammals are classified into three major groups:
- **Prototheria** (monotremes)
- **Metatheria** (marsupials)
- **Eutheria** (placental mammals)

2. **Identify the Characteristics of Monotremes**:
- Monotremes are a primitive group of mammals that lay eggs (oviparous) rather than giving birth to live young. They still retain some reptilian features.

3. **Examine the Given Options**:
- The options provided are:
- **Macropus** (kangaroo)
- **Ornithorhynchus** (platypus)
- **Baleonoptera** (blue whale)
- **Elephus** (elephant)

4. **Classify Each Option**:
- **Macropus (kangaroo)**: This belongs to Metatheria (marsupials).
- **Ornithorhynchus (platypus)**: This belongs to Prototheria (monotreme).
- **Baleonoptera (blue whale)**: This belongs to Eutheria (placental mammal).
- **Elephus (elephant)**: This also belongs to Eutheria (placental mammal).

5. **Identify the Correct Answer**:
- Among the options, **Ornithorhynchus (platypus)** is the only one that belongs to the monotreme group (Prototheria).

### Conclusion:
The correct answer is **Ornithorhynchus (platypus)**, which is a monotreme.

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