A label has a font - so if you want to use labels, you have to use 8 of them in order to get 8 different sizes.
There are a number of ways to do this: I would use perhaps spans?
Which will print as:
Will print as:
However, if you are trying to produce a program to do this, you will probably need to write code in the codebehind to generate the spans. It's not difficult, but as it's your homework, I think you have enough clues to get started, don't you?