instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
A collapsing nebula leads to nuclear fusion process.
answer:
A collapsing nebula leads to what process?


question:
When an atom gains or loses an electron it becames a(n) ion.
answer:
When an atom gains or loses an electron it becames an?


question:
In weather terms, the boundary between two air masses is called front.
answer:

In weather terms, what do you call the boundary between two air masses?