A. It is not unethical, because it is legal.
B. It is unethical because the files are being given for free.
C. Sharing copyrighted files without permission breaks copyright laws.
D. It is not unethical because the files are being given for free.
The correct answer to the question: "Why is it unethical to share copyrighted files with your friends?" is "Sharing copyrighted files without permission breaks copyright laws.".