I asked ChatGPT-3.5 (I'm not a ChatGPT-Plus subscriber so don't have access to ChatGPT-4) and it said: "Mary is the only sister mentioned in the question. Susan

I asked ChatGPT-3.5 (I'm not a ChatGPT-Plus subscriber so don't have access to ChatGPT-4) and it said: "Mary is the only sister mentioned in the question. Susan and her 7 brothers each have one sister, which is Mary. So Mary has 7 brothers and is the only sister in this scenario." This doesn't look to me like a perfect answer: it fails to notice what's either an inconsistency or a deliberately misleading question, and it makes an assumption I don't think it is justified in making. I think a perfect answer would be something like: "We haven't been told anything about who Mary is, so we have no idea how many sisters she has. Perhaps we are supposed to assume that she is one of the siblings described in the first sentence -- but if Mary and Susan are both female and not the same person, which seem like reasonable assumptions, then that is impossible because Susan's brothers have only one sister, who must be Susan and therefore cannot be Mary. If Mary is one of the siblings then one of those assumptions is false. In that case: If Mary and Susan are the same person, who is female, then Mary has no sisters. If they are different people and Mary is male despite the name, then Mary has one sister. If they are different people, Susan is not female despite the name, and Mary is female, then Mary must be the brothers' one sister, and she has no sisters. There are other even more tenuous ways to interpret the question -- perhaps Mary and/or Susan might be non-binary, or perhaps 'has one sister' means 'is attended by one nurse', or something -- but this answer is long enough already."