There are gold boxes, silver boxes and copper boxes on the table. There is a saying on the gold box: "Jewelry is not in this box", on the silver box: "Jewelry is in the gold box" and on the copper box: "Jewelry is not in this box". Now that only one of these three sentences is true, then. A. Jewelry is in a gold box B. Jewelry is in a silver box C. Jewelry is in a copper box D. Jewelry is not in any box.

Choose c, jewelry is analyzed in a copper box: only the first of these three sentences is true, that is, the sentence "jewelry is not in this box" written on the gold box is true. The words on the silver box and the copper box are not true, because according to the meaning of the question, the jewelry is in the copper box.