TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Optics explains the behavior of visible light and electromagnetic waves.

SOLUTION: What type of physics explains the behavior of visible light and electromagnetic waves?

PROBLEM: The reverse process of moving material into a cell is the process of exocytosis.

SOLUTION: The reverse process of moving material into a cell is the process of what?

PROBLEM: Some of the greatest concentrations of species are found in the tropics.

SOLUTION:
Where are some of the greatest concentrations of species found?