Final answer:
When you create an original work and put a Creative Commons attribution license on it, you are still the copyright holder. Registering with the U.S. Copyright Office is not required to be a copyright holder.
Step-by-step explanation:
If you create an original work and put a Creative Commons attribution license on it, you are still the copyright holder. The Creative Commons attribution license allows others to use, distribute, and modify your work, but they must give you credit as the original creator. Therefore, even though you have granted certain permissions to others, you still retain your copyright ownership.
Registering with the U.S. Copyright Office is not required to be a copyright holder. Copyright protection exists automatically from the moment the original work is fixed in a tangible form of expression. However, registering your work with the Copyright Office provides additional benefits, such as the ability to sue for infringement and claim statutory damages.