To solve this problem, we need to analyze each option and find the one that does not belong to the group:
- Tadpole: A tadpole is the larval stage of a frog; it indicates an immature state in the life cycle.
- Fledgling: A fledgling is a young bird that has just acquired its flight feathers; it is also a stage in the early life cycle but specifically relates to birds.
- Cub: A cub is a young carnivorous mammal such as a lion, bear, or wolf; it signifies an immature stage for mammals.
- Kitten: A kitten is a young cat; it signifies an immature stage for mammals, particularly felines.
We observe that Tadpole, Cub, and Kitten represent the young or immature stages of their respective species. In contrast, Fledgling is specific to birds and not a category applicable across multiple species in the same context.
Therefore, the odd one out is Fledgling.