You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For consistency, answers should be in all lower cased letters.
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Question: Category: POTPOURRI 
Clue: Imported into Brazil from Africa, these "killer" insects escaped the lab & bred with locals

Answer: bees


Question: Category: A PARIS CHRONOLOGY 
Clue: Paris was founded around 250 B.C. by the Celtic Parisii tribe, who built a settlement on an island in this river

Answer: the seine


Question: Category: "T.W." 
Clue: You might have learned to ride your bike with the help of these attachments

Answer:
training wheels