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

Ex Input:
Some materials have negative heats of solution; the dissolution of one of these solutes in water is called?

Ex Output:
Some materials have negative heats of solution; the dissolution of one of these solutes in water is called?

Ex Input:
Bile acids, needed to emulsify lipids, are stored in the body in the gallbladder.

Ex Output:
Where are bile acids, needed to emulsify lipids, stored in the body?

Ex Input:
Stringed instruments can help show the relationship between tension and frequencies in strings.

Ex Output:
Stringed instruments can help show the relationship between tension and what in strings?