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

Ex Input:
Three many families are known quarks divided into.

Ex Output:
How many families are known quarks divided into?

Ex Input:
The sun is considered the center of the solar system.

Ex Output:
What is considered the center of the solar system?

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?