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
Compression osteosynthesis heals fracture mandible by: 
Select and explain. 
A. Primary union with out callus formation, B. Secondary union with out callus formation, C. Compression union, D. All of the above
A: Primary union with out callus formation
Answer: A: Primary union with out callus formation 
Explanation: None