Which structures are most similar in birds and mammals based on their functions? air sacs in birds and rib cages in mammals air sacs in birds and mammary glands in mammals gizzards in birds and teeth in mammals crops in birds and teeth in mammals?

The right option is; Air sacs in birds and rib cages in mammals

Birds have relatively small lungs plus nine air sacs that play an important role in respiration. The air sacs allow a unidirectional flow of air through the bird lungs. In mammals, the ribs are the long curved bones that form the rib cage. The rib cage surrounds the chest and allows the lungs to expand and thus facilitate breathing by expanding the chest cavity.