Rule 1: Don't hurt beginners. Even if they ask you to...
Ultimately, the question is unanswerable, but depending on how it is phrased you can chip away at it.
Sometimes, someone will clamp down and refuse to move, thereby demonstrating that "aikido doesn't work." My answer to this is to point out all the openings created by clamping down, and demonstrate how being more fluid gives uke more opportunities, including perhaps the opportunity for a reversal.
Sometimes, someone will have a particular scenario in mind, and won't see how "aikido technique" would work in that situation. Here, I would walk through the scenario and show how aikido principles continue to apply even if what happens doesn't look like kihon waza.
If there's a more senior person available, you could demonstrate how trying to use strength grounds the attacker and is counterproductive, while a softer touch works. This demonstration can be risky with beginners because they have very little structure and are easy to throw the "wrong" way by mistake.
As a shodan, be aware that *your* aikido probably *doesn't* work in every situation that your students could dream up. "I don't know" is a better answer than confidently making a claim that you can't personally back up.