Final answer:
The residential areas established outside of downtown for middle-class Americans are known as suburbs option (a), offering a respite from urban issues and symbolizing middle-class affluence.
Step-by-step explanation:
The residential neighborhoods that were established outside of downtown areas for middle-class Americans who could afford to move there are known as suburbs. Following the industrialization period, middle-class families moved to suburbs which were connected to cities by improved transportation systems like horse-drawn or electrified streetcars.
These areas allowed residents to work in the city while escaping its noise, pollution, and crime each evening. The suburbs featured single-family homes, parks, and utilities, and gave their residents a sense of affluence, separating them economically and racially from the urban cores where economically disadvantaged African Americans, often in the form of the urban poor or rural migrants, remained.