Last two $({11}^{\mathrm{th}} \mathrm{and} {12}^{\mathrm{th}})$ pairs of ribs are different from all other ribs because 

• A

  Dorsally they are attached to the thoracic vertebrae

• B

  Intercostal muscles are not attached to them

• C

  They join the tenth rib with the help of hyaline cartilage

• D

  Ventrally they are attached neither to the sternum nor to the cartilages of other ribs