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: "D" IN SCIENCE 
Clue: Sharks first inhabited the waters during this period of the Paleozoic era named for an English county

Answer: devonian


Question: Category: MYTHOLOGY 
Clue: This Norse god known for his great strength was a protector of peasants & farmers

Answer: thor


Question: Category: WORLD MUSIC 
Clue: This "good girl gone bad" was discovered when a music producer heard her while on vacation in Barbados

Answer:
rihanna