A :

I believe/that regular exercise is important. Exercise helps us relax. I love jogging/in the early morning. I can enjoy the quiet and fresh air.

B :

I think/we need to get enough sleep/every day. Sleep improves our mental and physical health. I do better in school/when I sleep enough.

C :

Sorry to interrupt,/but you are missing an important point. A healthy diet is the most important thing/because our body is made of what we eat. I have more energy/when I eat a lot of fruit and vegetables.