Biologists suspect that feathers are modified scales. Ancient reptiles developed feathers as a way to insulate their bodies from the cold and regulate their body temperatures. However, many of these early feathered reptiles were unable to fly. Thus, today’s flightless birds probably developed their feathers as a way to manage their body temperatures.
The argument above relies on which of the following assumptions?
A. A characteristic developed for a particular ability does not remain after that ability is lost.
B. Some animals that are able to fly lack feathers.
C. Feathered dinosaurs that were able to fly also used their feathers to regulate body temperature.
D. Today’s flightless birds are direct descendants of feathered reptiles.
E. Without the ability to regulate their body temperature, flightless birds will go extinct.