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
Citric acid concentration in MTAD is: 
Select and explain. 
A. 4.25%, B. 3.75%, C. 1%, D. 0.50%
A: 4.25%
Answer: A: 4.25% 
Explanation: Composition

Tetracycline:

– It is bacteriostatic, broad spectrum antibiotic.
– It has low pH and acts as calcium chelator.
– It removes smear layer.
– It has property of substantivity. 
– It promotes healing.

Citric acid (4.25%): It is bactericidal in nature and removes smear layer.
Detergent (Tween 80): It decreases surface tension.