'A' makes an offer to 'B' who is standing on the other side of the river. 'B' accepts the offer aloud. In which of the following circumstances will the communication of acknowledgment of the offer against 'A' be considered complete?

• A. When 'B' answers but A has not heard the answer
• B. When 'A' informs 'B' that he has received the notice of acknowledgment
• C. When A listens to the statement made by 'B'
• D. none of the above