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: Sodium-potassium pumps help nerve cells establish a voltage across their plasma membranes.

Answer: Sodium-potassium pumps help nerve cells establish a voltage across their what?


Question: Microevolution is the process by which organisms change in small ways over time.

Answer: What is the process by which organisms change in small ways over time?


Question: The outer core is made of liquid metal.

Answer:
What is the outer core made of?