What prediction do the sector model and the concentric zone model make about a city's central business district (CBD)?

The CBD will have a relatively high proportion of residents to workers.
The CBD will retain a core of high-income workers throughout the life of the city.
The CBD will be the place of employment of the people who live in the closest residential areas.
The CBD will largely employ light-manufacturing and other low-skill workers.
The CBD will have a shifting mixture of banking, retail, and entertainment workers.