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Out of the mare Dorothy B. Jr. , Tenacious was sired by Challedon , the 1939 American Horse of the Year and U.S. Racing Hall of Fame inductee .
 U.S. Racing Hall of Fame
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 U.S. Racing Hall of Fame