Given a fact, create a question that can be answered using the fact. Construct the question such that it is unambiguous, has a unique answer and the answer can be given using the fact.

Q: Fact: weathering usually occurs over a period of many years

A: A stone is weathered into sand in about?
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Q: Fact: dissolving a substance in water causes the water to taste like that substance

A: A person has a glass of water and a friend pranks them by making their water taste different. They prankster added?
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Q: Fact: vaccines can help prevent illness

A:
Before their trip to the Amazon Bill and Jane had sharp metal objects stuck into their arms by a doctor.?
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