Ink/Unity issue: need random choices from a list of choices

Hi everyone!

I'm working on a project with Ink and Unity. I need to have three choices appear for the player, but they need to be three random choices from a list of twenty. Also, ideally there would never be the same choice listed more than once in a set of three and once a choice has been used it will not appear again during the game. I'm aware of the ~ or shuffle method for pseudo random choice and of the * for only showing a choice once, but that doesn't seem to have the choices talking to each other, so there's no way to guarantee that the same choice won't be listed twice. Does any of that make sense? I wish I could provide some sample code, but I have none since I haven't found anything that comes even remotely close to doing what I need. I really appreciate any help anyone can offer!