The author considers the Marxist sociologist' s thesis about the origins of racial prejudice to be______.

A．a greater concentration of middle-class residents in central cities
B．a sharp decline of the life quality in central cities
C．a boom in setting up factories and offices in central cities
D．a rapid development of public transportation

A．the revival of some North American and European CBDs
B．the problems facing the development of U.S. downtown areas
C．the moving pattern of the U.S. middle class
D．the possible solutions to the fiscal problems