What kinds of materials on the internet are protected by copyright law?

Any image, text, sound, and video with a copyright statement or $($c$)$ icon.

Essentially every image, text, sound, and video that has not specifically been released for public use by its legal owner.

Only those images, texts, sounds, and videos that have legally filed for copyright.

Essentially every image, text, sound, and video if it is on a $.$com domain.