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.

Q: Category: ASTRONOMY 
Clue: A galactic cloud of dust & gas, its name comes from the Latin for "cloud"

A: nebula
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Q: Category: RIVERS 
Clue: The mouth of this 2315-mile-long river lies in the Mississippi River 17 miles above St. Louis

A: the missouri
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Q: Category: PRESIDENTIAL VPs 
Clue: Thomas Jefferson

A:
john adams
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