instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
On a global scale, plants and other photosynthetic organisms have generated all of the oxygen in the air.
answer:
On a global scale, plants and other photosynthetic organisms have generated all of what element in the air?


question:
Cancer occurs most often in adults over fifty age.
answer:
Cancer occurs most often in adults over what age?


question:
Medium is the matter through which sound waves travel.
answer:
What is the matter through which sound waves travel?