instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Oxygen gas is given off by plants.
answer:
Which gas is given off by plants?

question:
The pupil is the name of the black opening in the eye that lets light enter.
answer:
What is the name of the black opening in the eye that lets light enter?

question:
Optics explains the behavior of visible light and electromagnetic waves.
answer:
What type of physics explains the behavior of visible light and electromagnetic waves?