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

Example Input: Processing of filtrate in the proximal tubule helps maintain the ph level in body fluid.
Example Output: Processing of filtrate in the proximal tubule helps maintain what level in body fluid?

Example Input: Line graphs are especially useful for showing changes over time.
Example Output: Line graphs are especially useful for showing changes over what?

Example Input: Biodiversity is a measurement of the amount of variation of the species in a given area.
Example Output:
What is a measurement of the amount of variation of the species in a given area called?