Pretty sure it's C. tighten and contract
Answer:
As a principal, I would make sure the students affected by bullying knew they could come to a teacher. Having a trusted adult is very important so that way the student could explain their situation. I would enforce consequences for the bullies. Also educating staff and students on the signs of bullying. Many children won't speak up if they are being bullied, which would decrease the likelihood of the bullying going unnoticed. Not only this but preventing the bullies themselves by teaching the consequences of bullying at a young age.
Explanation:
I currently have braces and at first they are going to cause a slight pain to your teeth, make sure you brush them even more then usual and more thoroughly, brush your teeth after each meal if possible.
B. Achieving something in a short period of time