Why Do Secondary Groups Often Distinguish Between Members and Leaders

Why do secondary groups often distinguish between members and leaders?

A) Because they want to reward people for becoming new members.
B) Because they worry that they may attract people who actually are seeking to undermine the group's goals, so they are hesitant to embrace new members.
C) Because strict hierarchies are known to generate more creative contributions from people in a group.
D) Because members are can easily leave, forcing leaders to do much of the organizational work.