When is an original work considered public domain? a. when posted via social media b. when it is posted on the internet c. when a copyright symbol is not included with the piece of work d. when explicit permission is given by the author / owner

The correct answer isn’t really a choice shown. I would choose D because if a work doesn’t have a copyright symbol that doesn’t mean it’s in the public domain. In a real life situation it would be best to ask the creator before you use their work. If they say it’s in the public domain then you’re fine, but even if they say you can use it that doesn’t mean it’s in the public domain, it just means that you have permission to use it.