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

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

A: Skeletal muscles must work in pairs to move bones back and forth at a joint because they can only do what?
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Q: Six many neutrons do 99% of carbon atoms have.

A: How many neutrons do 99% of carbon atoms have?
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Q: There are two different main types of diabetes.

A:
How many different main types of diabetes are there?
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