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: Lead sulfate is the white solid that forms on corroded battery terminals.

Answer: What is the white solid that forms on corroded battery terminals?


Question: Skeletal muscles must work in pairs to move bones back and forth at a joint because they can only contract.

Answer: Skeletal muscles must work in pairs to move bones back and forth at a joint because they can only do what?


Question: Galvanic cells kind of cells have positive cell potentials, and all the reduction reactions are reversible.

Answer:
What kind of cells have positive cell potentials, and all the reduction reactions are reversible?