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

[Q]: Compression zones is the opposite of rarefaction zones, where air molecules in waves are loosely packed.
[A]: What is the opposite of rarefaction zones, where air molecules in waves are loosely packed?

[Q]: Some compounds form rigid frameworks called crystals.
[A]: Some compounds form rigid frameworks called what?

[Q]: Depth and density influence the pressure of fluids.
[A]:
What two factors influence the pressure of fluids?