Answer:
What two letters in the alphabet say goodbye?
What has a head and a tail but no body?
The buyer doesn’t want it, the producer doesn’t need it and the user doesn’t know their using it.
There's one in every deck of cards and in a famous movie
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.
What sphinxes employ and players enjoy.