In the list of animals given below, hen is the odd one out. (human being, cow, dog, hen)
The reason for this is

Options

A. it undergoes internal fertilisation.
B. it is oviparous.
C. it is viviparous.
D. it undergoes external fertilisation.

Explanation

To determine why the hen is the odd one out in the list of animals (human being, cow, dog, hen), we can analyze the reproductive methods of each animal.

### Step-by-Step Solution:

1. **Identify the Animals**: The animals in the list are:
- Human being
- Cow
- Dog
- Hen

2. **Understand Reproductive Methods**:
- **Human Being**: Humans reproduce through internal fertilization and give birth to live young.
- **Cow**: Cows also reproduce through internal fertilization and give birth to live young.
- **Dog**: Dogs reproduce through internal fertilization and give birth to live young.
- **Hen**: Hens reproduce through external fertilization and are oviparous, meaning they lay eggs.

3. **Compare the Reproductive Methods**:
- The first three animals (human, cow, dog) are viviparous, meaning they give birth to live young after internal fertilization.
- The hen is oviparous, meaning it lays eggs after external fertilization.

4. **Conclusion**: The hen is the odd one out because it is the only animal in the list that lays eggs (oviparous), while the others give birth to live young (viviparous).

### Final Answer:
The reason the hen is the odd one out is that it is oviparous (lays eggs), while human beings, cows, and dogs are viviparous (give birth to live young).