This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skeletal System, Subject name: Radiology
An 8-year-old child presented with pain at shoulder and arm. A X-ray reveals a uniform well-defined lucent lesion at the metaphysis. Most likely diagnosis is?(AIIMS 2016) 
Select and explain. 
A. Simple bone cyst, B. Aneurysmal bone cyst, C. Giant cell tumour, D. Osteoid osteoma
A: Simple bone cyst
Answer: A: Simple bone cyst 
Explanation: Ans. A Simple bone cystLucent geographic lesion seen in humeral metaphysis in a child is most commonly a simple bone cyst. Trapdoor signQ/Fallen fragment signQ/Hinged fragment signQ may be seen.