Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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Question: You see a faster reaction rate when the concentration of reactants is higher.

Answer: What kind of reaction do you see when the concentration of reactants is higher?


Question: The refrigerator door contains iron of the following statements best explains why magnets usually stick to a refrigerator door.

Answer: Which of the following statements best explains why magnets usually stick to a refrigerator door?


Question: Lipids play several important roles in the human body.

Answer:
What play several important roles in the human body?