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

Ex Input:
The frequency of a wave is the reciprocal of the period of the wave.

Ex Output:
The frequency of a wave is the reciprocal of what other attribute of the wave?


Ex Input:
Pyramid ecosystem is used to show energy flow through the trophic levels.

Ex Output:
What is used to show energy flow through the trophic levels?


Ex Input:
The term analogous is used to describe structures that are similar in unrelated organisms.

Ex Output:
What term is used to describe structures that are similar in unrelated organisms?