What Does 'Consideration Need Not Be Adequate, but It Must

What does 'consideration need not be adequate, but it must be sufficient' mean?

A) The acts and promises must be of value in the eyes of the law, but need not be a 'good bargain'.
B) The acts and promises must be done at the request of the promisor.
C) A reasonable sum must be paid for the goods or services rendered.
D) A particular sum must be paid for the goods or services rendered.