One pair of wings occurs in

Options

A. Dragonfly
B. Housefly
C. Mayfly
D. Butterfly.

Answer

To determine which organism has one pair of wings, we can analyze the options provided:

1. **Identify the options**: The options given are dragonfly, housefly, mayfly, and butterfly.

2. **Understand the classification**: All these organisms belong to the phylum Arthropoda, specifically under the class Insecta. Insects typically have two pairs of wings, but there are exceptions.

3. **Examine each option**:
- **Dragonfly**: Dragonflies have two pairs of wings, one on the mesothorax and one on the metathorax. Therefore, this option does not fit the criteria.
- **Housefly**: Houseflies have one pair of functional wings. The second pair is reduced and modified into halteres, which serve as balancing organs during flight. This option fits the criteria.
- **Mayfly**: Mayflies also have two pairs of wings, so this option does not fit the criteria.
- **Butterfly**: Butterflies have two pairs of wings as well, thus this option does not fit the criteria.

4. **Conclusion**: Based on the analysis, the organism that has one pair of wings is the **housefly**.

### Final Answer:
The organism that has one pair of wings is the **housefly**.