The best way to respond when you don't know the answer to a question is to definitely let the person asking the question or the individual ask the question that you will do your upcoming research in order to come up with the best response and the best let me say action in order to answer that question because if they don't see that you're showing any kind of effort to even know the answer or understand the answer or even learn to better your knowledge then there's might as well just walk into anything and everything clues