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

Example Input: 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
Example Output: What celestial events are the source of elements heavier than iron?

Example Input: Passage: Heat waves have increased in frequency and duration in recent years. The summer 2011 North American heat wave brought record temperatures across the Midwestern and Eastern United States. Many states and localities broke records for temperature and for the most days above 100 o F. Answer: cell membrane
Example Output: What are all cells surrounded by?

Example Input: Passage: Solar energy is used to heat homes and water, and to make electricity. Scientists and engineers have many ways to get energy from the Sun ( Figure above ). One is by using solar cells. Solar cells are devices that turn sunlight directly into electricity. Lots of solar cells make up an individual solar panel. You may have seen solar panels on roof tops. The Sun's heat can also be trapped in your home by using south facing windows and good insulation. Answer: insulation
Example Output:
The sun's heat can also be trapped in your home by using south facing windows and good what?