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

[Q]: Light retains its original color under water because frequency remains the same when light is refracted.
[A]: Light retains its original color under water because what remains the same when light is refracted?


[Q]: Correlation is different from causation term that refers to the factor that is producing the effect.
[A]: Correlation is different from what term that refers to the factor that is producing the effect?


[Q]: The posterior end of a typical rib is called head.
[A]:
The posterior end of a typical rib is called what?