Final answer:
Ratites are flightless birds belonging to the Paleognathae clade, characterized by their primitive skeletal structure and absence of a keel on the sternum,the correct option is B).
Step-by-step explanation:
A ratite is a type of flightless bird that evolved from the dinosaur lineage and includes species such as the ostrich, kiwi, and emu.
Ratites belong to the Paleognathae clade, which diverged from other birds after the extinction of the dinosaurs during the Cenozoic era. As members of the Paleognathae, they are characterized by a more primitive skeletal structure, absence of a keel on the sternum (which flighted birds have to anchor powerful flight muscles), and generally large body sizes.
The evolutionary lineage of ratites does not include perching birds, toothed birds from the Cretaceous period like the Enantiornithes, or the early Cretaceous bird Archaeopteryx.