----- and ------- pairs of ribs are called the floating ribs.

Hint: Rib cage is the cage of bones in the body. It cannot be eaten by then animals. They are the long curved bones used to protect the heart and lungs. They give lungs the space to expand and relax while inhaling and exhaling.

Complete step-by-step answer:
Ribs are the part of the vertebral column. There are 12 pairs of ribs in our body. The flat bones which are dorsally connected to vertebral sternum make the rib cage. These bones are very thin. On the ventral side, they are connected to the sternum.
Ventrally they are attached to the sternum by hyaline cartilage. Thoracic vertebrae, ribs and sternum together form the rib cage.
The ventrally attached rib pairs are from one to ten. The last two pairs that are ${11^{th}}$ and ${12^{th}}$ are called floating rib pairs as they are not attached ventrally to the sternum.
Sometimes people have one more pair of ribs, the $13^{th}$ pair, called gorilla ribs because they are like distant cousins of humans, gorillas. They will form the extra floating ribs.
The ${11^{th}}$ and ${12^{th}}$ pairs of ribs are the floating ribs, rarely someone has the 13 pair which is the extra floating rib. Slipping/ hypermobility of these ribs can also be painful.

Note: Ribs can be broken by a traumatizing attack by some object or sudden movement by the body. Ribs are usually not eaten but form the leftovers of the non-vegetarian food. They are the long curved bones. A rib has a head, neck and body connecting the head with the body.