Answer:
What has many teeth but can't bite?
I am a rock group with four members all of whom died in plane crashes. Who am I?
A large oasis in the desert. Come with cash and leave with none.
I am put on the table, cut, but never eaten. What am I?
Mr. and Mrs. Mustard have five daughters and each daughter has one brother. How many people are there in the Mustard family?
No matter how little or how much you use me, you change me every month.