Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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Question: When light passes from one medium to another, it changes speed.

Answer: When light passes from one medium to another, it changes what?


Question: Deep currents are caused by differences in density at the top and bottom of the ocean.

Answer: What is caused by differences in density at the top and bottom of the ocean?


Question: Sediment is transported by currents.

Answer:
How is sediment transported?