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

[EX Q]: Yeast fermentation causes holes in bread.
[EX A]: What causes holes in bread?

[EX Q]: Some plants have stolons, or stems, that run along the ground and are commonly called runners.
[EX A]: Some plants have stolons, or stems, that run along the ground and are commonly called what?

[EX Q]: When gas particles collide, these collisions are considered elastic.
[EX A]:
When gas particles collide, what kinds of collisions are these considered?