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: OPERAS BY CONTINENT 
Clue: "Aida "

Answer: africa


Question: Category: EXPRESSIONS 
Clue: This positive expression used since the 1940s promotes a type of stove

Answer: "now you\'re cooking with gas"


Question: Category: PLENTY OF TIME 
Clue: The theory of relativity says the existence of time depends on the presence of this, from the Latin for "room"

Answer:
space