The correct option is B 8th, 9th and 10th pair of ribs
There are 12 pairs of ribs in the human body. The ribs which are dorsally connected to the thoracic vertebrae and ventrally connected to the sternum are called true ribs.
But the 8th, 9th and 10th pair are connected ventrally to the 7th rib by a cartilage and not to the sternum directly. Thus they are called false ribs.