Which Is NOT an Assumption of Social Identity Theory

Which is NOT an assumption of social identity theory?

A) People are motivated to achieve through feelings of competition with outgroup members.
B) People derive a sense of self-esteem from their social identity as members of an
Ingroup.
C) People's self-concepts are partly dependent on how they evaluate the ingroup
Relative to other groups.
D) People categorize the world into ingroups and outgroups.