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 patient presents with compound fracture of Tibia with 1 cm opening in skin. Which grade it belongs? 
Select and explain. 
A. Grade I, B. Grade II, C. Grade IIIA, D. Grade IIIB
A: Grade I
Answer: A: Grade I 
Explanation: A i.e. Grade I