15/15 
Here's another great question to add onto the quiz:
Which sorority has this badge restriction?
(to my knowledge, this is the only NPC sorority with this restriction, but I could be mistaken)
"No other pin, badge, insignia, such as a fraternity pin, Greek letter indicating the name of a chapter or a symbol denoting an office, may be attached to the badge in any way, whether by a chain or by hanging it on the fastener."
Teensy hint: It's not Delta Gamma, but I will tell you that it's a 3 lettered NPC