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: Dental
Phoenix abscess is 
Select and explain. 
A. Reversible pulpits., B. Acute apical periodontitis, C. Acute exacerbation of an existing chronic inflammation, D. Chronic abscess
C: Acute exacerbation of an existing chronic inflammation
Answer: C: Acute exacerbation of an existing chronic inflammation 
Explanation: None