The correct answer is A. 16.
There are 12 pairs of ribs in the human body, which are connected to the spine at the back and to the sternum (breastbone) at the front. The first seven pairs of ribs are called true ribs because they are attached directly to the sternum. The next five pairs of ribs are called false ribs because they are not attached directly to the sternum. The last two pairs of ribs are called floating ribs because they are not attached to the sternum at all.
The ribs protect the organs in the chest, such as the heart and lungs. They also help with breathing by expanding and contracting the chest cavity.
The number of ribs can vary from person to person. Some people may have an extra rib, or they may be missing one. This is usually not a problem, but it can sometimes cause pain or other health problems.