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 are typical and acceptable preventive and therapeutic measures for dealing with the periodontal problems during fixed appliance therapy? 
Select and explain. 
A. Elimination of gingivitis prior to placing orthodontic appliances, B. Home care instruction regarding the use of the toothbrush and water pik during orthodontic treatment, C. Megavitamin therapy, D. Scaling and curettage immediately after appliance removal
A: Elimination of gingivitis prior to placing orthodontic appliances
Answer: A: Elimination of gingivitis prior to placing orthodontic appliances 
Explanation: None