In the Publish-Subscribe messaging model, the subscribers register themselves in a topic and are notified when new messages arrive to the topic. Which pattern does most describe this model?

In the Publish-Subscribe messaging model, the subscribers register th

1.	In the Publish-Subscribe messaging model, the subscribers register themselves in a topic and are notified when new messages arrive to the topic. Which pattern does most describe this model?
A.	adapter
B.	notifier
C.	observer
D.	factory
Answer» D. factory