Onion peel appearance is seen in-

Ans. is 'a' i.e., Ewing's sarcoma * Onion - peel periosteal reaction is characteristically seen in Ewing's sarcoma.* Note - Onion peel periosteal reaction may also be seen rarely in osteosarcoma.Other Radiological features of Ewing's sarcoma* Diaphyseal* Mottled or moth eaten lesion* Sunray appearance (More common with osteosarcoma)* Codman's triangle (More common with osteosarcoma)