Which of the following subway announcements are attempts to establish or enforce a social norm?
a. “Loud music and phone conversations are discourteous to fellow riders. Please keep the noise down.”
b. “If you see something, say something.”
c. “Please watch your step as you exit. Be careful of the gap between the train and the platform edge.”
d. “Please be patient and allow others to exit the train before you attempt to enter.”
e. “The train is being held at the station due to traffic ahead. We apologize for the inconvenience.”