Explanation:

- Among the given options (a) Pigeon, (b) Parrot, (c) Kiwi, and (d) Eagle, the bird that cannot fly is the Kiwi.
- The Kiwi is a flightless bird native to New Zealand.
- Let's discuss the reasons why the Kiwi cannot fly in more detail.

Physical Characteristics:
- The Kiwi is a small, round bird with a long beak and a stout body.
- Its wings are extremely small and almost non-functional, making them incapable of generating enough lift for flight.
- The Kiwi's wings are more like tiny stubs that are hidden under its feathers.
- The bird's body structure and wing development are not adapted for flying.

Evolutionary Adaptations:
- Over millions of years, the Kiwi's ancestors evolved in an environment without significant land predators.
- As a result, they gradually lost their ability to fly because they didn't need to escape from airborne predators.
- Instead, they developed strong legs and claws, which are ideal for running and digging.

Terrestrial Lifestyle:
- Kiwis have adapted to a terrestrial lifestyle, residing mainly on the forest floor.
- They are excellent runners and can reach speeds of up to 20 miles per hour.
- The Kiwi's strong legs allow it to navigate through dense vegetation and dig burrows for nesting.

Nocturnal Behavior:
- Kiwis are nocturnal birds, meaning they are most active during the night.
- They have a keen sense of smell and use their long beak to search for food, which primarily consists of insects, worms, and fruits.

Conclusion:
- In conclusion, among the given options, the Kiwi is the bird that cannot fly.
- Its small, non-functional wings, evolutionary adaptations, terrestrial lifestyle, and nocturnal behavior all contribute to its inability to fly.

C