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

Example Input: The ileocecal valve, a sphincter, is usually in a constricted state, but when motility in the ileum increases, this sphincter relaxes, allowing food residue to enter the first portion of large intestine.
Example Output: The ileocecal valve, a sphincter, is usually in a constricted state, but when motility in the ileum increases, this sphincter relaxes, allowing food residue to enter the first portion of what?

Example Input: Light retains its original color under water because frequency remains the same when light is refracted.
Example Output: Light retains its original color under water because what remains the same when light is refracted?

Example Input: Exercising regularly is a good health habit.
Example Output:
Which activity is a good health habit?