The costalcailages of these ribs do not reach the sternum -

Ans. is'd'i.e., 8th, 9th& 10thRibsThere are 12 pairs of ribs.All aiculate posteriorly with thoracic veebrae.The ribs are divided into two types.True ribs or veebrosternal ribs :- These are 1st to 7th ribs which aiculate directly with sternum through costal cailages.False ribs :- These are 8th to 12th ribs and do not aiculate directly with sternum.False ribs can be divided into:Veebrochantral ribs:- 8th, 9th and 10th ribs whose costal cailages aiculate with each other and with 7th costal cailage forming costal marginFloating ribs veebral ribs :- 11th and 12th ribs have free anterior ends