Concept:Flight adaptations in birds mainly reduce weight, improve body shape, or supply power for flying.
Explanation:Birds have hollow or light bones that lower their body weight, making flight easier.
Their streamlined body shape cuts air resistance during flight.
Powerful chest muscles provide the strong wing beats needed to stay airborne.
Clawed digits, however, are not a flight adaptation.
Claws help birds perch, walk, climb, or catch prey.
They do not contribute directly to the mechanics of flying.
Therefore, clawed digits are the exception among the listed features.
Answer:D. clawed digits