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Birds, reptiles, and mammals, are all amniotes and are distinguished from amphibians by having eggs which are terrestrially adapted, and are protected by means of amniotic membranes.

Archaeopteryx has characteristics of both maniraptoran dinosaurs and modern birds. Traits in skeletons of Archaeopteryx like those of a dinosaur included a jaw with teeth and a long bony tail. Like birds, it had feathers modified for flight, both on the forelimbs and on the tail, a trait associated only with birds among modern animals. Hence, option (b) is the correct answer.

a. Neornithes

Neornithes refer to the modern birds and the descendants from their most recent common maniraptoran ancestor. Hence, option (a) is the incorrect answer.

c. Enantiornithes

Enantiornithes means 鈥渙pposite birds,鈥� which refers to the fact that certain bones of the shoulder are joined differently than the way the bones are joined in modern birds. Hence, option (c) is the incorrect answer.

d. Paleognathae

The Paleognathae are a group of flightless birds including ostriches, emus, rheas, and kiwis. Hence, option (d) is the incorrect answer.