Final Answer:
Syndication feeds are one way of announcing the availability of a 4) podcast.
Step-by-step explanation:
Podcast (Option 4): Syndication feeds, such as RSS (Really Simple Syndication), are commonly used to distribute and announce the availability of podcasts. These feeds allow users to subscribe to podcasts, receive updates, and automatically download new episodes when they are released.
Backlink (Option 1): A backlink is a hyperlink from one webpage to another. While syndication feeds may be used to distribute content, they are not specifically designed to announce the availability of backlinks.
Gigapop (Option 2) and Mirror Disk (Option 3): These terms are unrelated to syndication feeds or podcast distribution. A Gigapop typically refers to a high-performance internet exchange point, and a mirror disk is a storage device for duplicating data.
Option 4 is the answer.