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

Input: Consider Input: A bow wake is created when the wave source moves faster than the wave propagation speed.

Output: What is created when the wave source moves faster than the wave propagation speed?


Input: Consider Input: If two populations do not mate and produce fertile offspring, separate species result.

Output: If two populations do not mate and produce fertile offspring, what results?


Input: Consider Input: Paper cup object has the greatest flexibility.
Output: Which object has the greatest flexibility?