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

A hookworm is classified as a parasite.
A hookworm is classified as what type of organism?

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?

A wall of rocks or concrete a called a groin.
What is a wall of rocks or concrete called?