Interestingly, it did not give "fou" as an option when I cheated. I used "dingue" and got marked wrong. Of course, that's what I get for cheating, but it was still weird to have it offer three incorrect options.
can one not use 'bête' here instead of 'fou'?
No, "c'est bête" means (roughly) "that's a pity".
But you can use: "c'est dingue !" (amazing)
Ah. I thought 'bête' meant silly.
C'est la folie ?