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: HOSPITALS 
Clue: The Cleveland Clinic tops U.S. News' 1996 ranking of hospitals in this, the study of the heart

Answer: cardiology


Question: Category: "HARD" QUESTIONS 
Clue: Stubborn

Answer: hard-headed


Question: Category: TAKE YOUR VITAMINS 
Clue: Your liver converts beta-carotene into this vitamin

Answer:
vitamin a