Final answer:
The two principal families of carnosaurs are the (Option c) Allosauridae and Tyrannosauridae, both of which are theropod dinosaurs within the larger clade known as Archosaurs.
Step-by-step explanation:
The two principal families of carnosaurs are the Allosauridae and Tyrannosauridae. These distinguished groups are part of the larger clade known as theropods, which are characterized by their bipedal stance and often predatory nature. The Allosauridae family includes the well-known Allosaurus, a large theropod that roamed during the Late Jurassic period. The Tyrannosauridae family is famous for including Tyrannosaurus rex, one of the most iconic dinosaurs, which existed during the Late Cretaceous period.
Coming under the umbrella of the Archosaurs, which also include modern birds and crocodilians, these two families belong to the Saurischia ("lizard-hipped") dinosaurs. It is fascinating to note that birds are the descendants of small, feathered maniraptoran dinosaurs within the Saurischia, not the Ornithischia ("bird-hipped") despite what the name might suggest.