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

[Q]: 2 hydrogen, 1 oxygen atoms combine to make up a molecule of water.
[A]: What atoms combine to make up a molecule of water?


[Q]: Incubation is when birds keep their eggs warm while the embryos inside develop.
[A]: What is it called when birds keep their eggs warm while the embryos inside develop?


[Q]: Particle accelerators can nuclear fusion in stars be simulated.
[A]:
How can nuclear fusion in stars be simulated?