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

Q: A collapsing nebula leads to nuclear fusion process.

A: A collapsing nebula leads to what process?
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Q: Sodium-potassium pumps help nerve cells establish a voltage across their plasma membranes.

A: Sodium-potassium pumps help nerve cells establish a voltage across their what?
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Q: The simplest type of battery contains single cell.

A:
The simplest type of battery contains what?
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