The correct option is C Scales on their hind limbs
The characteristic feature which indicates that birds have reptilian ancestry is the presence of scales on their hind limbs
The digestive system of reptiles is similar to that of all higher vertebrates whereas the bird's digestive is the crop, the proventriculus, and the gizzard.
Birds lay hard-shelled calcareous eggs, but most reptiles lay soft-shelled ones.
Most reptiles have 3 chambered heart whereas birds have a four chambered heart.