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

[Q]: Limestone is insoluble in water, so acid can dissolve it.
[A]: Limestone is insoluble in water, so what can dissolve it?


[Q]: The energy stored in the organic molecules of food ultimately comes from the sun.
[A]: The energy stored in the organic molecules of food ultimately comes from where?


[Q]: The development of the respiratory system in the fetus begins at about 4 weeks.
[A]:
The development of the respiratory system in the fetus begins at about?