The graphic concept that best illustrates the concept of social stratification is d: pyramid.
A pyramid is the most appropriate graphic concept to illustrate the concept of social stratification because it effectively conveys the hierarchical nature of social classes. The base of the pyramid represents the lowest social class, while the apex represents the highest social class. The layers in between represent the intermediate social classes.
A pyramid is suitable for illustrating social stratification. A pyramid's shape naturally depicts a hierarchical structure, with each layer representing a different level of social standing.