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

The core of a star collapses during a supernova, forming a neutron star.
The core of a star collapses during what event, forming a neutron star?

Most have cells that are not able to exchange gases with the outside environment do multicellular organisms need transport systems.
Why do multicellular organisms need transport systems?

Saprotrophs are decomposers that feed on the organic matter left over from other decomposers.
What are decomposers that feed on the organic matter left over from other decomposers?