Which would violate copyright

1. citing the source of information that you used in your paper.
2. making copies of a picture and selling them without permission from the creator.
3.buying a painting that you did not make from it's creator.
4. creating your own music and distributing it

2. making copies of a picture and selling them without permission from the creator.

how do you know

I know because making copies of a protected work, such as a picture, without permission from the creator infringes on their exclusive rights to reproduce and distribute their work. This would be a violation of copyright law.