Answer:
When one does not know what it is, then it is something; but when one knows what it is, then it is nothing.
What gets whiter the dirtier that it gets?
If four people can repair four bicycles in four hours, how many bicycles can eight people repair in eight hours?
A piece of paper that determines the academic fate of kids everywhere.
What divides by uniting and by dividing?
A cowboy rode into Friday. He stayed in town for three days and rode back on friday. How is that possible?