No one wants to confess that he/she is ignorant on any given subject. Saying “I don’t know” is simply unacceptable. And what could be worse than admitting your lack of knowledge during a job interview.
I watch a nomination hearing conducted by the Senate Armed Services Committee. There sat the nominee, being grilled by the Senators, in that unfortunate condition of not knowing the answer. Was he phased?–Not visibly. He had a response which he frequently gave. The most brilliant answer: “I have not been briefed.”
I love it! That simple phrase can be adapted to nearly any circumstance. I will rely on it as necessary from now on and recommend my readers do the same.
And if, by some stretch of the imagination, “I have not been briefed” does not suit your situation, you can reply: Je ne sais pas and impress your listener with your vast knowledge of the French language.