In this task, you're given an open-domain question. Your task is to provide an answer to the given question. There is only one unique answer for each question. Your answer should be short, and refer to an entity, date, number, etc. Do not put your answer in the context of a sentence.
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Question: Where does the earth's magnetic field originate?

Answer: Earth's core


Question: Who is the original singer of nothing compares to you?

Answer: Prince Rogers Nelson


Question: When did the guy who played robbie rotten die?

Answer:
21 August 2018