instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Equinox comes halfway between the two solstices. At equinoxes, the Sun's rays shine most directly at the Equator ( Figure below ). The daylight and nighttime hours are exactly equal on an equinox. The autumnal, or fall, equinox happens on September 22 or 23. The vernal, or spring, equinox happens March 21 or 22 in the Northern Hemisphere. Answer: equinox
answer:
What event occurs between the two solstices?

question:
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
answer:
What happens to old oceanic crust at convergent boundaries?

question:
Passage: Unlike sponge adults, sponge larvae can swim. They have cilia that propel them through the water. As larvae develop and grow, they become more similar to an adult sponge and lose their ability to swim. Answer: cilia
answer:
What helps to propel sponge larvae through the water?