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

Combustion reaction occurs when a substance reacts quickly with oxygen.
What occurs when a substance reacts quickly with oxygen?

Ribosomes are the only organelles that prokaryotic cells have.
What are the only organelles that prokaryotic cells have?

Volcanic gases helpe to form the atmosphere on earth.

What did volcanic gases help to form on earth?