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: Surgery
A 19 yrs old male has a small circumscribed sclerotic swelling over diaphysis of femur, likely diagnosis is: 
Select and explain. 
A. Osteoclastoma, B. Osteosarcoma, C. Ewing's sarcoma, D. Osteoid osteoma
D: Osteoid osteoma
Answer: D: Osteoid osteoma 
Explanation: Sclerotic lesion over diaphysis of a long bone in a young patient indicative of osteoid osteoma. Ref: Essential Ohopedics By Maheshwari 2nd Edition, Page 213