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

Ex Input:
The mesopause is at the top of the mesosphere.

Ex Output:
What is at the top of the mesosphere?


Ex Input:
Atoms of metals are good conductors of electricity because they give up electrons.

Ex Output:
Why are atoms of metals good conductors of electricity?


Ex Input:
Acting like drawstrings to close off the alimentary canal, the sphincter regulates the passage of material between compartments.

Ex Output:

Acting like drawstrings to close off the alimentary canal, what regulates the passage of material between compartments?