A hydroelectric power plant produces energy from flowing water.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Concept of Hydroelectric Power:**
- A hydroelectric power plant generates electricity by converting the energy of flowing water into electrical energy.

2. **Water Reservoir:**
- Water is collected in a reservoir, which acts as a storage for potential energy. This stored water is at a height, giving it potential energy due to gravity.

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