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

Ex Input:
Processing of filtrate in the proximal tubule helps maintain the ph level in body fluid.

Ex Output:
Processing of filtrate in the proximal tubule helps maintain what level in body fluid?


Ex Input:
Plankton is the most common life form in the ocean.

Ex Output:
What is the most common life form in the ocean?


Ex Input:
Exchange occurs directly with the external environment in unicellular organisms type of organisms.

Ex Output:
Exchange occurs directly with the external environment in what type of organisms?