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: WHADDYA DRINKIN'? 
Clue: A Greyhound is vodka & this tart juice

Answer: grapefruit juice


Question: Category: SONGS OF THE '60S 
Clue: Louis Armstrong's only No. 1 hit, it hit the charts for 19 weeks in 1964

Answer: "hello, dolly!"


Question: Category: WORLD HISTORY 
Clue: For most of the 15th century this Indian empire ruled over what's now Mexico

Answer:
aztec empire