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

Q: The newest, outer layers of secondary xylem are called sapwood.

A: What are the newest, outer layers of secondary xylem called?
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Q: If the amount of force of that is applied is increased, it is easier happens to the work that a machine is producing.

A: If the amount of force of that is applied is increased, what happens to the work that a machine is producing?
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Q: Oil is the most commonly used source of energy in the world.

A:
What is the most commonly used source of energy in the world?
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