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
Which of the following antibiotics is NOT indicated for periodontal therapy? 
Select and explain. 
A. Erythromycin, B. Metronidazole, C. Tetracycline, D. Augmentin
A: Erythromycin
Answer: A: Erythromycin 
Explanation: None