Hey there! Hello!
For this problem, I'm pretty convinced that your answer is B. The main purpose of tracking changes on a document is to see what changes you've made and be able to go back to before you made certain changes. B sounds the most like that.
A and D are pretty much the same and don't really capture what tracking changes is for.
C doesn't really have to do with tracking changes and more about the document itself.
Hope this helped you out! Feel free to ask me any additional questions if you have any.
