If an officer makes a stop or arrest based on a person's race or ethnicity, it is an example of...

The correct answer is B, racial profiling. Racial profiling refers specifically to the practice where law enforcement makes decisions about stopping, searching, or arresting individuals based on their race or ethnicity, rather than on any specific evidence of wrongdoing. This practice is widely regarded as unjust and discriminatory because it assumes guilt based on characteristics unrelated to actual criminal behavior.

Racial profiling undermines trust between communities and law enforcement and can perpetuate negative stereotypes. It is important for law enforcement agencies to apply the law impartially, ensuring that actions taken are based on behavior or credible information rather than superficial characteristics.

Other options, while related to discrimination within law enforcement, do not capture the precise nature of acting upon race or ethnicity. Selective enforcement typically refers to the practice of enforcing certain laws more strictly than others, which can stem from various motivations and may or may not involve race. Discriminatory policing is a broader term that encompasses various forms of bias in law enforcement but does not specifically pinpoint the act of stopping individuals based solely on race or ethnicity. Personal bias indicates a more subjective viewpoint but does not fully encompass the systemic issue of racial profiling in policing practices.