What one question with an answer of either yes or no can the nurse ask of the native will permit her to take the safe jar?

Answer 1

Heh, this answer is actually the answer to most of these riddles.

I don't know this one exactly, but I guess she has to choose between one that is safe and one that is poisoned and she can ask one question, right?

Well, since most of these riddles contain two person you can ask the same question and one tells the truth and one tells a lie, the logic tells that if you ask both which is the safe one they will both point to different jars. Darn, ain't getting further that way.

So, to make it easy on ya. One will always tell the truth and one will always lie. So you ask them: Which jar would the other pick? The one telling the truth would point to the jar the lying one would pick, being the jar with poison. The one who is always lying would be forced to point to the exact same jar as the one telling the truth, because he can't say the truth and point to the jar without the poison.

Understandable? hehe, I know it's a bit out there, but that's the only answer I've come up with to all these riddles :)