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

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


[Q]: Induced or spontaneous are the two methods in which mutations arise in dna.
[A]: What are the two methods in which mutations arise in dna?


[Q]: Bouyant force is the upward force exerted by fluids when any object, such as a boat, is placed in it.
[A]:
What is the upward force exerted by fluids when any object, such as a boat, is placed in it?