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
Commonest site of fracture leading to fat-embolism is: 
Select and explain. 
A. Tibia, B. Femur, C. Humerus, D. Ulna
B: Femur
Answer: B: Femur 
Explanation: B i.e. Femur