Answer:
What is it that you must give before you can keep it
What kind of cup doesn't hold water?
Without coolant, you'll have some trouble with this.
No matter how little or how much you use me, you change me every month. What am I?
Handy when you need to measure something or run a kingdom.
As round as an apple. As deep as a cup. All the king's horses can't pull it up.