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: PARTICLE PHYSICS 
Clue: To get an element's mass number, add its protons & these

A: neutrons
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Q: Category: WHAT THE "H" 
Clue: To celebrate the bicentennial of Andrew Jackson's birth, Lyndon Johnson visited this mansion in March 1967

A: the hermitage
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Q: Category: BALLET 
Clue: Mental illness ended his career after he choreographed his last ballet, "Till Eulenspiegel"

A:
vaclav nijinsky
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