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

Input: Consider 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

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

Input: Consider Input: Passage: Refracting and reflecting telescopes are optical telescopes that use lenses to gather light. Answer: light

Output: Refracting and reflecting telescopes are optical telescopes that use lenses to gather what?

Input: Consider Input: Passage: Arachnids also have two additional pairs of appendages. Describe these two pairs. Answer: 2
Output: How many additional pairs of appendages do arachnids have?