पसलियों की अन्तिम दो युग्मों को फ्लोटिंग रिब्स कहा जाता है क्योंकि

Explanation

The eleventh and twelfth parirs of are known as floating ribs.
They are not attached to the sternum or cartilage of sternum.
They are attached only to the vertebral column and are floating ribs.