Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: Figure 23.30 Virtually all aquatic organisms depend directly or indirectly on protists for food. (credit "mollusks": modification of work by Craig Stihler, USFWS; credit "crab": modification of work by David Berkowitz; credit "dolphin": modification of work by Mike Baird; credit "fish": modification of work by Tim Sheerman-Chase; credit "penguin": modification of work by Aaron Logan). Answer: protists
Output:
Virtually all aquatic organisms depend directly or indirectly on what for food?