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

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

A: What celestial events are the source of elements heavier than iron?
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Q: Passage: In many ways, humans are unique among mammals. For example, we have bigger brains and a greater ability to learn than any other species in the mammalian class. In many ways, however, we are typical of the mammalian order to which we belong. That order is the Primate Order. To fully understand what it means to be human, you need to know more about this fascinating order of mammals. Answer: humans

A: What mammalian class has the greatest ability to learn?
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Q: Passage: The axes of rotation of the planets are mostly nearly perpendicular to the orbital plane. Answer: nearly perpendicular

A:
How do planets usually rotate to their orbital planes?
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