According to contract law, basic requirements for offer and acceptance must be met for an agreement of purchase and sale to be valid. Which one of the following is NOT one of those requirements?"

Answer choices:

A. The offer must be made to one or more persons or corporation or to the public in general.

B. The offer may be revoked or withdrawn prior to acceptance, subject to certain limitations.

C. The offer may be revoked by either party after acceptance, subject to certain exceptions.

D. The offer must remain open for acceptance by the other party for a reasonable amount of time.