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]: Duplicating the results of an experiment process will most likely lead to the scientific acceptance of a hypothesis.
[EX A]: Which process will most likely lead to the scientific acceptance of a hypothesis?

[EX Q]: Oxygen gas is given off by plants.
[EX A]:
Which gas is given off by plants?