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

Example Input: Plasma matter makes up most of the universe.
Example Output: What type of matter makes up most of the universe?

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: Smooth muscle regulates air flow in lungs.
Example Output:
Which kind of muscle regulates air flow in lungs?