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


[Q]: A healthy diet is the best way to maintain a strong, fit body.
[A]:
Which is the best way to maintain a strong, fit body?