Given a statement and question, generate the answer to the question such that the answer is contained in the statement.
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Question: statement: muscles contracting cause a person's arm to straighten, question: What causes a person's arm to straighten?

Answer: muscles contracting


Question: statement: Scales give fish more acceleration., question: What gives fish more acceleration?

Answer: Scales


Question: statement: x-rays are used in research, question: What is used in research?

Answer:
x-rays