Answer:
What can you catch but never throw?
I am green and ugly and come out at night with a crumple old broom. Who am I?
What is black when it is clean and white when it is dirty?
When one does not know what it is, then it is somethingอพ but when one knows what it is, then it is nothing.
What kind of room has no doors or windows?
What is always coming but never arrives?