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: THE ROTARY CLUB 
Clue: On an airplane they're "fixed"; on a helicopter they're actually "rotary"

Answer: wings


Question: Category: THE HISTORY OF THE WORLD: PART 1 
Clue: This event on October 8-9, 1871 forced thousands of Illinois residents to flee their homes

Answer: chicago fire


Question: Category: SCIENCE & NATURE 
Clue: Developed by astronomer A.E. Douglass, dendrochronology determines age in this way

Answer:
counting tree rings