The one could imply that of the alternates only one choice is possible, or permitted. Which alone could indicate several choices from the set of alterates could be selected in various. Which one is grammatically correct or better?

Understanding the Context

I have two assignments, one of them is done. I have two assignments, one of which is done. I watched a video tutorial that the teacher said. Both a/an and one mean one.

Key Insights

The difference is that one puts more emphasis on the number such as i have 4 computers and a printer/i have 4 computers and only one printer.