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

Ex Input:
Light retains its original color under water because frequency remains the same when light is refracted.

Ex Output:
Light retains its original color under water because what remains the same when light is refracted?

Ex Input:
Socket secures teeth in the mouth.

Ex Output:
What secures teeth in the mouth?

Ex Input:
The stratosphere is the heat source.

Ex Output:
What part of the atmosphere is the heat source?