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

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

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


Input: Consider Input: Fermat’s principle states that light will always take the path of the least amount of time.

Output: Fermat’s principle states that light will always take the path of least amount of?


Input: Consider Input: Some of the greatest concentrations of species are found in the tropics.
Output: Where are some of the greatest concentrations of species found?