Social psychologists suggest that the reason stereotypes are automatically activated is that they become and are thus spontaneously activated when we encounter a member or members of a stereotyped group. a. increasingly complicated b. impossible to change c. increasingly negative d. overlearned

I believe the answer is: overlearned

In psychology, overlearning refers to the act of practicing a new actions well beyond initial mastery (no room for improvement)
Overlearning could be perpetuated by individual will or majority's will and might influence a certain treatment toward a specific social group.