Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Q: Starches are complex carbohydrates that are the polymers of glucose.

A: What complex carbohydrates are the polymers of glucose?
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Q: A change of season and less food usually cause certain animals to migrate.

A: Which two environmental changes usually cause certain animals to migrate?
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Q: Memory t cells are long-lived and can even persist for lifetime long.

A:
Memory t cells are long-lived and can even persist for how long?
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