Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[Q]: Cancer occurs most often in adults over fifty age.
[A]: Cancer occurs most often in adults over what age?


[Q]: During the early paleozoic, the amount of carbon dioxide in the atmosphere was much greater compared to today.
[A]: During the early paleozoic, the amount of carbon dioxide in the atmosphere compared to today was?


[Q]: A heterocyclic compound contains atoms of two or more different elements in its ring structure.
[A]:
What type of compound contains atoms of two or more different elements in its ring structure?