Give an example of plant growth promoter.

Explanation

### Step-by-Step Solution:

1. **Understanding Plant Growth Promoters**: Plant growth promoters, also known as phytohormones or plant growth regulators, are substances that stimulate plant growth and development. They can be classified into two categories based on their action: stimulatory and inhibitory.

2. **Identifying Stimulatory Hormones**: The main plant growth promoters include:
- **Auxins**
- **Cytokinins**
- **Gibberellins**
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