Which one is not vestigial ?

Options

A. Wings of kiwi
B. Flipper of seal
C. Coccyx in man
D. Splint bone of horse

Answer

To determine which organ is not vestigial, we need to understand what vestigial organs are. Vestigial organs are those that were once useful in an organism's ancestors but have lost their original function in the modern organism.

Let's analyze the options provided:

1. **Wings of the Kiwi**:
- Kiwis are flightless birds, and their wings are not used for flying. Hence, the wings of the kiwi are considered vestigial.

2. **Flippers of Seal**:
- Seals use their flippers for swimming. Since these flippers serve a functional purpose in the animal's current lifestyle, they are not vestigial.

3. **Coccyx in Man**:
- The coccyx (or tailbone) is a remnant of a tail that was present in our ancestors. Although it no longer serves its original purpose, it is still present in humans, making it a vestigial organ.

4. **Splint Bone in Horses**:
- The splint bone was used for balance in the ancestors of horses. In modern horses, it no longer serves a significant function, which classifies it as a vestigial organ.

After analyzing all the options, we conclude that the **flippers of the seal** are not vestigial because they are functional and essential for swimming.

### Final Answer:
The organ that is not vestigial is the **flippers of the seal**.