This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharynx, Subject name: ENT
Most common cause of chronic retropharyngeal abscess 
Select and explain. 
A. Infective foreign body, B. Caries teeth, C. Caries of cervical spine, D. Suppuration of retropharyngeal lymph node
C: Caries of cervical spine
Answer: C: Caries of cervical spine 
Explanation: CHRONIC RETROPHARYNGEAL ABSCESS (PREVEEBRAL ABSCESS) AETIOLOGY :- It is tubercular in nature and is the result of (i) caries of cervical spine or (ii) tuberculous infection of retropharyngeal lymph nodes secondary to tuberculosis of deep cervical nodes. Ref:- Dhingra; pg num:-266,267