What statement about the fair use principle is true?

The fair use principle allows limited use of copyrighted material without obtaining permission from the copyright owner, primarily for purposes such as criticism, comment, news reporting, teaching, scholarship, or research. Whether a specific use qualifies as fair use depends on four factors: the purpose and character of the use, the nature of the copyrighted work, the amount and substantiality of the portion used, and the effect of the use on the market for the original work. Fair use is not a blanket exemption; it is determined on a case-by-case basis.