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

Passage: Most chemical reactions in organisms take place in an environment that is mostly water. Answer: water
The environment where most chemical reactions in organisms takes place consists mostly of what?

Passage: It's much easier to precisely make mirrors than to precisely make glass lenses. For that reason, reflectors can be made larger than refractors. Larger telescopes can collect more light. This means that they can study dimmer or more distant objects. The largest optical telescopes in the world today are reflectors. Telescopes can also be made to use both lenses and mirrors. Answer: destroyed
What happens to old oceanic crust at convergent boundaries?

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
What celestial events are the source of elements heavier than iron?