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

Example Input: Deep currents are caused by differences in density at the top and bottom of the ocean.
Example Output: What is caused by differences in density at the top and bottom of the ocean?

Example Input: Wave amplitude and wavelength are two important measures of wave size.
Example Output: Wave amplitude and wavelength are two important measures of what?

Example Input: The name for membrane-bound sacs that function in storage and transport is vacuoles.
Example Output:
What is the name for membrane-bound sacs that function in storage and transport?