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

[EX Q]: The action of flushing the toilet, performed multiple times daily, is the single biggest use of water in the home.
[EX A]: What action, performed multiple times daily, is the single biggest use of water in the home?

[EX Q]: Fractional crystallization is the separation of compounds on the basis of their solubilities in a given solvent.
[EX A]: What is the separation of compounds on the basis of their solubilities in a given solvent?

[EX Q]: Replace another in a molecule happens to atoms during a substitution reaction.
[EX A]:
What happens to atoms during a substitution reaction?