This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bone Tumour, Subject name: Orthopaedics
[{'content': "Soap bubble appearance is seen in \nSelect and explain. \nA. Giant cell tumour, B. Osteogenic sarcoma, C. Ewing's sarcoma, D. Osteoid osteoma", 'role': 'user'}, {'content': 'Answer: A \nExplanation: (Giant cell tumour) (181 -Apley\'s 8th)* Soap-bubble appearance due to ridging of the surrounding bone in Giant cell tumourX-Ray Appearance* Osteosarcoma - Sunray appearance**, Codman\'s triangle tumour new bone* Ewing\'s tumour - Onion - peel appearance*** Chondrosarcoma - Mottled calcification within the tumour* Simple Bone cyst - Well defined lobulated, radio lucent zone in the metaphysis or diaphysis of bone* Osteo chondroma - Large lesion shows "Cauliflower " appearance and degeneration and calcification in the centre of the cartilage cap', 'role': 'assistant'}]