Final answer:
Atticus's closing argument is a powerful plea for justice and equality, directly challenging the themes of prejudice and racism, in line with option C.
Step-by-step explanation:
Atticus's closing argument in 'To Kill a Mockingbird' profoundly addresses the themes of prejudice, racism, and equality. His argument does not support racism or discrimination; rather, it promotes justice, equality, and squarely challenges the prevailing prejudices of the time. The option that best summarizes Atticus's closing argument in relation to these themes is C. Atticus's argument challenges prejudice and is a plea for the jury to consider the evidence objectively, without the influence of their racial biases. It calls on the ideals of justice and the belief that everyone is equal before the law. By doing this, Atticus's argument becomes a central piece of the narrative that tackles these important themes head-on.