TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Fractional crystallization is the separation of compounds on the basis of their solubilities in a given solvent.

SOLUTION: What is the separation of compounds on the basis of their solubilities in a given solvent?

PROBLEM: The cardiovascular system in the human body consists of the heart, a network of blood vessels, and blood.

SOLUTION: Which system in the human body consists of the heart, a network of blood vessels, and blood?

PROBLEM: The sporophyte phase is the longest phase in the life of a(n) gymnosperm.

SOLUTION:
The sporophyte phase is the longest phase in the life of what?