The answer is A. Feathers.
Feathers are a type of integumentary structure that is found in birds. They are made of keratin, the same protein that makes up hair and nails in humans. Feathers are used for flight, insulation, and camouflage.
Tentacles are elongated, flexible appendages that are found in many different animals, including octopuses, squid, and jellyfish. Tentacles are used for sensing, grasping, and feeding.
Scales are small, flat, overlapping plates that are found on the skin of many different animals, including fish, reptiles, and birds. Scales are used for protection, camouflage, and temperature regulation.
Pseudopodia are temporary, finger-like projections that are used for movement and feeding by some protists.
Flagella are long, whip-like structures that are used for movement by some bacteria and protists.
The word that is different from the rest is feathers. Feathers are not found on all of the animals listed. They are only found in birds. The other four words are found on a variety of animals.