system
A chat on subreddit /r/me_irl
human
It's a paradox,  by choosing which one is right, you thus prove it wrong, there for all answer are neither right or wrong.

[EDIT: Thanks for all the up votes]
gpt
This is the right answer because 25% is up there twice. Which gives you a 50/50 probability of answering correctly which is only up there one time which is 25% which is up there twice and over and over again.