Final answer:
Option b) Cars gradually but inevitably replaced horses as a means of transportation, best expresses the central idea which details the transformation from horse-driven to auto-driven society and its profound effects.
Step-by-step explanation:
The central idea of the passage which describes the evolution of transportation can best be expressed by the option: b) Cars gradually but inevitably replaced horses as a means of transportation. This encapsulates the transformative impact automobiles had on society, shaping cities, economies, and the environment. The passages discuss the progression from horse-driven carriages to automobiles and how this technological advancement facilitated changes in city layouts, work commutes, and expanded the reach of where people could live and work.