Respiratory system I think. I MAY BE WRONG.
Hope I helped!
It will help you build muscle for sure but you will need to increase the reps if you want to improve further, it helps to build your biceps, pectoralis, and your deltoids
600 calories, hope that helps
I would tell them to tell a trusted adult and use a helpline like nsvrc.org as a resource. Be there to support them during the aftermath as it will take a toll on their mental health.