There are many townsmen associations and alumni associations all over the world. Which basic assumption of Tajfel's social identity theory does it reflect?
选项：

A:Part of an individual’s self-concept depends on how others evaluate the group to which that person belongs.;
B:Humans categorize people into in-group and out-group. ;
C:Individual’s self-esteem comes from social identification of group members.;
D:Identity is a process of establishing contact between an individual and another person or between an individual and another group.