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: Pathology
Internal resorption is characterised by 
Select and explain. 
A. Pain on percussion, B. Slow dull continuous pain, C. No characteristic feature, symptom free, D. Increased pulpal pain when lying down
C: No characteristic feature, symptom free
Answer: C: No characteristic feature, symptom free 
Explanation: None