External fertilization takes place in frogs.

Explanation

**Step-by-Step Solution:**

1. **Understanding Fertilization**: Fertilization is defined as the fusion of male and female gametes, which results in the formation of a diploid cell known as a zygote.

2. **Types of Fertilization**: There are two main types of fertilization:
- **Internal Fertilization**: This occurs inside the female body, where the male and female gametes fuse.
- **External Fertilization**: This occurs outside the female body, typically in an external environment such as water.

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