Do you ever get frustrated by your audience's questions? Have you heard the same question 40 times already?
Just keep this in mind: While you may have heard it 40 or 100 or 200 times, it's the first time they've asked it.
They don't know that you find it annoying, and they're not trying to annoy you on purpose. All they want is an answer.
Understand that everyone is in a different place and they can only know what they know at any given time.
But here's a hint: If you keep getting the same "dumb" question over and over, maybe it's your problem and not theirs.
Try to find a way to incorporate the answer into your presentation so they won't have to ask it any more!
What annoys you about your audience, and what can you tweak to fix it?