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

Virtually all aquatic organisms depend directly or indirectly on protists for food.
Virtually all aquatic organisms depend directly or indirectly on what for food?

Elements are pure substances that make up all matter.
Elements are pure substances that make up what?

Hormones send signals through your body.

Hormones send what through your body?