Your heart， lungs， and liver are all very important， and luckily you’ve got ribs to keep them safe. Ribs act like a cage of bones around your chest. It’s easy to feel the bottom of this cage by running your fingers along the sides and front of your body， a few inches below your heart. If you breathe in deeply， you can easily feel your ribs right in the front of your body， too. Some thin kids can even see a few of their ribs right through their skin.
　　Your ribs come in pairs， and the left and right sides of each pair are exactly the same. Most people have 12 pairs of ribs， but some people are born with one or more extra ribs， and some people might have one pair less.
　　All 12 pairs of ribs attach （固定） in the back to the spine （脊椎）， where they are held in place by the thoracic vertebrae （胸骨）. The first seven pairs of ribs attach in the front to the sternum， a strong bone in the center of your chest that holds those ribs in place. The remaining sets of ribs don’t attach to the sternum directly. The next three pairs are held on with cartilage （软骨） to the ribs above them.
　　The very last two sets of ribs are called floating ribs because they aren’t connected to the sternum or the ribs above them. But don’t worry， these ribs can’t ever float away. Like the rest of the ribs， they are securely attached to the spine in the back.
　　阅读选择
　　1. We have got ribs to keep safe.
　　A. heart， and liver B. heart， and lungs
　　C. heart， lungs， and liver
　　2. How many ribs do most people have？
　　A. 12 B. 24 C. 36
　　3. pairs of ribs are attached to the sternum.
　　A. 14 B. 10 C. 7
　　4. Why are the very last two sets of ribs called floating ribs？
　　A. Because they are connected to the sternum above them.
　　B. Because they aren’t connected to the sternum or the ribs above them.
　　C. Because they are connected to the ribs above them.