Why are the first seven pairs of ribs called true ribs?

They are attached dorsally to the thoracic vertebrae and ventrally to the sternum with the help of hyaline cartilage.

The correct answer is Option (3) –They are attached dorsally to the thoracic vertebrae and ventrally to the sternum with the help of hyaline cartilage.

There are 12 pairs of ribs. Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum. It has two articulation surfaces on its dorsal end and is hence called bicephalic. First seven pairs of ribs are called true ribs. Dorsally, they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage. The 8th, 9th and 10th pairs of ribs do not articulate directly with the sternum but join the seventh rib with the help of hyaline cartilage. These are called vertebrochondral (false) ribs. Last 2 pairs (11th and 12th) of ribs are not connected ventrally and are therefore, called floating ribs. Thoracic vertebrae, ribs and sternum together form the rib cage.