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

[EX Q]: Deep currents are caused by differences in density at the top and bottom of the ocean.
[EX A]: What is caused by differences in density at the top and bottom of the ocean?

[EX Q]: Fires, mainly caused by lightning, are a natural disturbance in temperate grasslands.
[EX A]: Fires, mainly caused by what, are a natural disturbance in temperate grasslands?

[EX Q]: The sun is the largest body in the solar system.
[EX A]:
What is the largest body in the solar system?