You are not required to answer any questions at all. Where youre from, where you were, what you did, nothing, however it may result in an inspection of your bags, so it depends on whether your interpretation of liberty is based on personal convenience.
Disclosure: ive done this opt-out twice. The first time I got to sit in a room with a few other folks who had been randomly selected based on their winning complexion, and was let go after 20 minutes and a bag search. The second time the screening room was busy so i was let go immediately. at no point did i answer a single question.