Final answer:
B) music by an existing band
Copyright infringement occurs when music by an existing band is used without authorization, violating artists' economic rights protected by law.
Step-by-step explanation:
The example from the student's question that can be considered a violation of copyright is B) music by an existing band if it is copied, distributed, or used without permission.
Copyright laws are in place to protect creators from unauthorized use of their work.
For instance, when music is illegally downloaded, it infringes upon the economic rights of artists and record labels, as supported by the ruling in the Supreme Court case MGM Studios v. Grokster (2005).