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: 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: Comparing genome sequences provides clues to evolution and development.

Answer: Comparing what sequences provides clues to evolution and development?


Question: Carbon dioxide does not rise like other gases because it has a density greater than air.

Answer:
Carbon dioxide does not rise like other gases because it has a density greater than what?