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 simplicity, answers should be in all lower cased letters.
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Question: Category: RAIDERS 
Clue: John J. Pershing's attempts to stop this Mexican raider included the U.S. cavalry's "last charge"

Answer: pancho villa


Question: Category: VIVA MEXICO! 
Clue: President from 2000 to 2006, this "sly" guy had formerly been president of Coca Cola de Mexico

Answer: fox


Question: Category: CLASSICAL MUSIC 
Clue: In 1818, Heinrich Stolzel took out a patent on this horn improvement allowing changes of pitch

Answer:
stolzel valve