Briefly compare the occurrence of ribs and sternum in the following groups: fishes, amphibians, reptiles, birds, and mammals.
a) Ribs and sternum present in all groups
b) Ribs present, sternum absent in all groups
c) Ribs and sternum absent in fishes; ribs present, sternum absent in amphibians; ribs and sternum present in reptiles, birds, and mammals
d) Ribs and sternum absent in all groups
