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

Urea is made in the liver and excreted in urine.
What is made in the liver and excreted in urine?

Changing the shape of an elastic material gives it potential energy.
Changing the shape of an elastic material gives it what type of energy?

Photoautotrophs and chemoautotrophs are two basic types of autotrophs.
Photoautotrophs and chemoautotrophs are two basic types of what?