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: Radiology
First radiological sign in acute osteomyelitis is: 
Select and explain. 
A. Soft tissue swelling, B. Periosteal reaction, C. Sequestrum, D. Involucrum
A: Soft tissue swelling
Answer: A: Soft tissue swelling 
Explanation: Soft tissue swelling