Which of the following is a flightless bird?

Options

A. Neophron
B. Struthio
C. Psittacula
D. Pavo

Answer

To determine which of the given options is a flightless bird, we can analyze each option based on the characteristics of flightless birds:

1. **Neophrons**: This refers to the genus that includes the Egyptian Vulture, which is capable of flight. Therefore, this is not a flightless bird.

2. **Struthio**: This is the scientific name for the ostrich, which is well-known as a flightless bird. Ostriches have lost the ability to fly due to their large size and adaptations for running.

3. **Cetacula**: This is not a commonly recognized name for any bird species. It may refer to a genus or species that is not flightless.

4. **Pavo**: This refers to the peacock, which is capable of flight, although it is not a strong flier. Therefore, this is also not a flightless bird.

Based on this analysis, the flightless bird among the options provided is **Struthio** (the ostrich).

### Step-by-Step Solution:
1. **Identify the Options**: The options given are Neophrons, Struthio, Cetacula, and Pavo.
2. **Understand Flightless Birds**: Flightless birds lack the adaptations necessary for flight, such as a keel on the sternum for muscle attachment and hollow bones.
3. **Analyze Each Option**:
- Neophrons: Capable of flight.
- Struthio: Known as the ostrich, a flightless bird.
- Cetacula: Not recognized as a flightless bird.
- Pavo: Capable of flight (peacock).
4. **Conclusion**: The only flightless bird in the options is **Struthio**.