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Which of the following best completes the passage below? A recently discovered manuscript, estimated to be around 3000 years old, was analyzed by historians revealing it to be a record of a trade between two ancient clans. Supported by corroborating artifacts, the manuscript details how the Kintaro clan offered agricultural products in exchange for 150 decorative masks, believed to be essential for their rituals, which were provided by the Tashira clan. However, it has been established that the latter clan lacked the skills to create any items other than simple pottery until 1500 years ago, so __________.