Answer: D. Multiple nuclei model
Step-by-step explanation:
Edward Ullman helped develop this model of urbanization.
Cities generally have a Central Business District (CBD) that forms the basis for housing and development in the city. It is referred to as the nucleai because it is very important and usually in the middle.
The model developed by Edward Ullman, called for multiple CBDs with some located on the outskirts so that they would be closer to those who live in the suburbs outside the city.