This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
[{'content': 'Histology of unicameral bone cyst -a) Blood filled cavitiesb) Endothelial liningc) Giant cellsd) Bone formation \nSelect and explain. \nA. cd, B. bc, C. bd, D. ac', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Simple bone cyst contains clear fluid and consists of flimsy fibrous lining, often containing giant cells.\nThere is osteoclastic resorption of adjacent bone, (i.e., endosteal osteoclastic resorption) with periosteal new bone formation.', 'role': 'assistant'}]