Why is Gambusia introduced into drains and ponds?

Explanation

### Step-by-Step Solution:

1. **Understanding Gambusia**: Gambusia is a type of fish commonly referred to as mosquito fish. It is known for its ability to consume mosquito larvae.

2. **Problem of Mosquitoes**: In urban areas, stagnant water in drains and ponds provides an ideal breeding ground for mosquitoes. Female mosquitoes lay their eggs in these stagnant waters, leading to rapid population growth.

3. **Health Risks**: The increase in mosquito populations poses significant health risks as mosquitoes are vectors for various diseases. For example, they can transmit malaria, dengue, chikungunya, and filariasis.

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