When the GM asks, "Are you sure about that?", is such an overused meme that, unless your character has a specific advantage of 'common sense' or the like, it's likely a red-herring of some sort. All my best gaming experiences have been achieved by answering "Are you sure about that with:
Yes
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--m(^0^)m-- Wot, no sig?
Yes
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--m(^0^)m-- Wot, no sig?