In which of the following animals external fertilisation occurs?

Options

A. Rat
B. Frog
C. Duck
D. Lizard

Answer

To determine which of the following animals undergoes external fertilization, we need to understand the concept of fertilization and the specific reproductive methods of the given animals.

### Step-by-Step Solution:

1. **Understanding Fertilization**:
- Fertilization is the process where male and female gametes (sperm and egg) fuse to form a zygote.
- There are two types of fertilization: internal and external.
- **Internal Fertilization**: Occurs inside the female's body.
- **External Fertilization**: Occurs outside the female's body, usually in a water medium.

2. **Identifying the Animals**:
- The animals listed in the question are:
- Red (likely referring to a red fish or similar aquatic animal)
- Duck
- Frog
- Lizard

3. **Analyzing Each Animal**:
- **Red (Fish)**: Many fish species undergo external fertilization, where eggs and sperm are released into the water.
- **Duck**: Ducks typically have internal fertilization, where the male fertilizes the eggs inside the female.
- **Frog**: Frogs are known for external fertilization. The female lays eggs in water, and the male fertilizes them outside her body.
- **Lizard**: Lizards generally reproduce through internal fertilization.

4. **Conclusion**:
- Among the options, the frog is the most well-known example of an animal that undergoes external fertilization. The process involves the female laying eggs in water, where the male then fertilizes them.

### Final Answer:
The animal in which external fertilization occurs is **Frog** (Option B).

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