Final answer:
Atticus compares racism to a disease by expressing hope that his children, Jem and Scout, won't catch the racism that is prevalent in Maycomb, highlighting its potential to spread and affect people much like a contagious illness.
Step-by-step explanation:
Atticus in To Kill a Mockingbird metaphorically compares racism to a disease in several ways. He does this by suggesting that racism is contagious and can spread rapidly (A), by expressing hope that Jem and Scout won't "catch" Maycomb's usual disease of racism (B), and by commenting on how otherwise reasonable people seem to go crazy when racial issues arise, much like insanity (suggesting C). However, the best answer to how Atticus metaphorically compares racism to a disease is by expressing hope that Jem and Scout won't "catch" Maycomb's usual disease (B), as it directly relates to the idea of disease being spread and possibly prevented.