TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Fires, mainly caused by lightning, are a natural disturbance in temperate grasslands.

SOLUTION: Fires, mainly caused by what, are a natural disturbance in temperate grasslands?

PROBLEM: It takes about one year for earth to orbit the sun.

SOLUTION: Which of these takes about one year to complete?

PROBLEM: Oxygen is transferred into the bloodstream by simple diffusion.

SOLUTION:
How is oxygen transferred into the bloodstream?