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

Input: Consider Input: A collapsing nebula leads to nuclear fusion process.

Output: A collapsing nebula leads to what process?


Input: Consider Input: Diffraction is the phenomenon in which light and sound waves become circular at the point source of a barrier.

Output: What is the phenomenon in which light and sound waves become circular at the point source of a barrier?


Input: Consider Input: Scientists explain the world based on observations.


Output: Scientists explain the world based on what?