Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: Potential energy is energy that is stored in a person or object. Answer: potential energy
[EX A]: Energy that is stored in a person or object is called?

[EX Q]: Passage: Figure 32.21 Supernovas are the source of elements heavier than iron. Energy released powers nucleosynthesis. Spectroscopic analysis of the ring of material ejected by Supernova 1987A observable in the southern hemisphere, shows evidence of heavy elements. The study of this supernova also provided indications that neutrinos might have mass. (credit: NASA, ESA, and P. Challis). Answer: supernovas
[EX A]: What celestial events are the source of elements heavier than iron?

[EX Q]: Passage: There are three types of mechanical waves. They differ in how they travel through a medium. The three types are transverse, longitudinal, and surface waves. All three types are described in detail below. Answer: three
[EX A]:
How many types of mechanical waves are there?