Given a scientific question, generate a correct answer to it.

Input: Consider Input: What "kind" of water may take longer to become contaminated than surface water, while the natural cleaning process may take longer?

Output: groundwater

Input: Consider Input: What is the term for a substance that increases the rate of a chemical reaction but is not changed or used up in the reaction?

Output: a catalyst

Input: Consider Input: The food particles are caught by the collar of the choanocyte and brought into the cell by what process?
Output: phagocytosis