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

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:
Mechanical waves term describes waves that travel through matter.

Ex Output:
What term describes waves that travel through matter?


Ex Input:
Gases is less dense then either solids or liquids.

Ex Output:

What is less dense then either solids or liquids?