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: LET'S GET SMALL 
Clue: In area, it's the smallest constitutional monarchy in the world

Answer: monaco


Question: Category: MUSICAL GROUPS 
Clue: This outspoken rap group led by Chuck D. took its name from a song title that ended "Number One"

Answer: public enemy


Question: Category: BMW 
Clue: (Cheryl)  With test flights in the early 1940s, BMW pioneered this radical type of engine

Answer:
the jet engine