美国的零售商行业，在这十年来，发生了前所未有的变化。
Retailers in the us have seen a decade of unprecedented change.
有了这个元素，周期表会发生前所未有的变化——延伸出新的一行。
With that addition the table will do something which has never happened before. It will grow a new row.
今天，在通讯，交通，计算机技术前所未有的变化注入了新的动力。
Today, unprecedented changes in communications, transportation, and computer technology have given the process new impetus.
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