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: MATHLETES 
Clue: John Nash has a beautiful mind that contributed to this "theory" of strategic decision making

Answer: game theory


Question: Category: 20th CENTURY ART 
Clue: Russian-born artist whose work is seen here:

Answer: marc chagall


Question: Category: NATURAL WONDERS 
Clue: First measured in 1852 & called Peak XV, it's 1.65 miles taller than the tallest mountain in North America

Answer:
mount everest