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

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

[Q]: Fermat's principle states that light will always take the path of the least amount of time.
[A]: Fermat's principle states that light will always take the path of least amount of?

[Q]: Oxygen has increased in the atmosphere throughout the history of the earth.
[A]:
What has increased in the atmosphere throughout the history of the earth?