TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: A 50 ml graduated cylinder of the following tools would give the most precise measurement of 15 milliliters of water.

SOLUTION: Which of the following tools would give the most precise measurement of 15 milliliters of water?

PROBLEM: Virtually all aquatic organisms depend directly or indirectly on protists for food.

SOLUTION: Virtually all aquatic organisms depend directly or indirectly on what for food?

PROBLEM: Protists are thought to be the oldest eukaryotes.

SOLUTION:
What is thought to be the oldest eukaryotes?