科研之友
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<正>口香糖香香甜甜有嚼劲,既可吃又可玩,很多人都喜欢。你知道是谁发明了口香糖吗?Did you know that the invention of chewing gum was an accident? People have been chewing gum-like substances since the early times. Some were made from resin, a substance that comes from plants. Others were made from
