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

Example Input: Filter feeders called rotifers collect digestive and excretory wastes in cloacal bladder primitive organ.
Example Output: Filter feeders called rotifers collect digestive and excretory wastes in what primitive organ?

Example Input: Cancer occurs most often in adults over fifty age.
Example Output: Cancer occurs most often in adults over what age?

Example Input: An infection may be intracellular or extracellular, depending on this?
Example Output:
An infection may be intracellular or extracellular, depending on this?