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
The sterility of the root canal during treatment is assessed by 
Select and explain. 
A. Radiographs, B. Clinical observations, C. Bacterial cultures, D. Colour of dressings
C: Bacterial cultures
Answer: C: Bacterial cultures 
Explanation: None