A. The publisher waits for a subscriber, who then consumes it. However, the publisher will time out if no consumer arrives within the given timeout period.

B. The publisher sends the message. However, it is never consumed because there wasn't anything listening when it arrived, regardless of the message timeout length.

C. The publisher successfully sends a message, which will be consumed later, once there is a subscriber, assuming the message hasn't timed out.

D. The message publisher is immediately notified about the lack of subscribers and can decide for itself if, and when, to resend.