According to my research on studies conducted by various sociologists, I can say that based on the information provided within the question this illustrates the impact of our social identities on prejudice. Social Identity an individual's self-concept derived from perceived membership in a relevant social group, and since ingroup bias is described as being prejudice or preferring a specific group while discriminating others we can say this is the answer.
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It depends, normally it's C. Most people refer that too the status, income and the owned property of the person being referred too. Society is constantly changing however, and maybe someday that'll change.