Which of these statements about the Publisher-Subscriber pattern utilized by Cloud Pub/Sub is TRUE?

Publisher applications can receive messages from a topic.
Subscriber applications can subscribe to a topic to receive the message when the subscriber is ready.
Publisher applications can send messages to a subscriber.
Subscriber applications can send messages on a topic directly to publisher applications.

The correct answer is:

Subscriber applications can subscribe to a topic to receive the message when the subscriber is ready.