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
During extraction of the upper first molar, the mesio buccal root is missing and is suspected to have been pushed into the maxillary sinus.
To classify a chronic oral antral communication what time duration is acceptable? 
Select and explain. 
A. 7 days, B. 14 days, C. 21 days, D. 28 days
B: 14 days
Answer: B: 14 days 
Explanation: None