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

Through tubular ducts part do exocrine glands discharge their contents.
Through what part do exocrine glands discharge their contents?

Fractional crystallization is the separation of compounds on the basis of their solubilities in a given solvent.
What is the separation of compounds on the basis of their solubilities in a given solvent?

Different media affect the speed of light.
Different media affect what property of light?