Bone in bone appearance is seen in-

Ans. is 'c' i.e., Osteopetrosis * Bone within a bone is a descriptive term applied to bones that appear to have another bone within them.* Bone within a bone appearance is seen in : - Normal neonate, Prostaglandin El therapy, Growth arrest/recovery lines n Heavy metal (e.g., Lead) poisoning, Bisphosphonate therapy, Hypothyroidism & Hypoparathyroidism, Sickle cell anemia n Hypercalcemia & Hypervitaminosis D, Osteopetrosis, Rickets / Osteomalacia (healed phase), Acromegaly, Scurvy (healed phase).