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I would find it unlikely that anyone would ask, but in the event that they did I would just say something like “I had some personal matters to deal with and needed to take a little extra time to get everything done that semester.” It seems like a fairly minor thing in the big scheme of things. (Not suggesting that your problems were minor, but the fact that you overcame them responsibly and quickly resulted in only a tiny bump in your record (the “BI” on your transcript)).</p>