The quiz in RH124 chapter 6, section 2 does not have a correct answer for question 7:
The answer is not "Primary group" . . . or at the very least it is misleading in that "primary group" is used to mean the group's name. The fourth field in /etc/passwd is the GID, as stated in chapter 6, section 1...
...and in the man pages:
Program Lead at Arizona's first Red Hat Academy, est. 2005 Estrella Mountain Community College