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

Example Input: The double helix dna shape forms when the two nucleotide chains wrap around the same axis.
Example Output: What distinctive dna shape forms when the two nucleotide chains wrap around the same axis?

Example Input: Three many families are known quarks divided into.
Example Output: How many families are known quarks divided into?

Example Input: Skeletal muscles must work in pairs to move bones back and forth at a joint because they can only contract.
Example Output:
Skeletal muscles must work in pairs to move bones back and forth at a joint because they can only do what?