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 consistency, answers should be in all lower cased letters.
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Question: Category: NAME THAT CENTURY 
Clue: President McKinley is assassinated

Answer: the 20th century


Question: Category: NONFICTION 
Clue: This minister's "The Purpose-Driven Life" was the top nonfiction bestseller of both 2003 & 2004

Answer: rick warren


Question: Category: CAPITAL IDEA 
Clue: Long before it was a capital, this city on the Thames River was a communications center

Answer:
london