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

A collapsing nebula leads to nuclear fusion process.
A collapsing nebula leads to what process?

Gravity makes soil and rock particles move gradually down the slope during each thaw.
What makes soil and rock particles move gradually down the slope during each thaw?

Photosynthesis occurs in the chloroplast.

In which part of a plant cell does photosynthesis occur?