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

[Q]: Exotic species are also called invasive species because they threaten other species.
[A]: Why are exotic species also called invasive species?


[Q]: Wave amplitude and wavelength are two important measures of wave size.
[A]: Wave amplitude and wavelength are two important measures of what?


[Q]: Protons and neutrons are located in the central nucleus.
[A]:
Where are protons and neutrons located?