I prefer to spend my free time alone.
Why do you prefer to spend time alone?
I'm really busy and there are so many things that I have to do. My friends are a distraction.
It's great that you can appreciate alone time, but you should also try to balance your time alone with your time with friends. If you spend too much time by yourself, then your relationships may stagnate and they may not be there when you need them.
I'm busy, I need to study for my test. That's it, bye.
I can understand how you would like alone time it is always good to have sometimes. There should be a balance though between how much time you spend alone and then with friends. Spending time with friends can help you relax more so you can do better in other areas of life.