TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Lichens are not a single organism, but rather an example of a mutualism.

SOLUTION: Lichens are not a single organism, but rather an example of a what?

PROBLEM: Destructive interference in waves occurs two troughs what things overlap.

SOLUTION: Destructive interference in waves occurs when what things overlap?

PROBLEM: Compounds like sodium chloride form structures called crystals.

SOLUTION:
Compounds like sodium chloride form structures called what?