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

[Q]: A fewer predators is most likely to cause the number of rabbits living in an area to increase.
[A]: Which factor is most likely to cause the number of rabbits living in an area to increase?


[Q]: The seven unique crystal types are defined by faces parts of themselves (parts that intersect at various angles).
[A]: The seven unique crystal types are defined by what parts of themselves (parts that intersect at various angles)?


[Q]: In the past, asteroids colliding with planet earth has caused many organisms to die off.
[A]:
In the past, what colliding with planet earth has caused many organisms to die off?