Which theory suggested that cities grow in a circular fashion?
a. peripheral model
b. multiple nuclei model
c. sector model
d. concentric zone model

Sector model theory suggested that cities grow in a circular fashion

Thus Option D is the right answer.

Explanation:

Concentric Circle growth model is first envisaged by Ernest Burgess who specifies that urban settlements of Chicago are based on this pattern. It starts with the central commercial region in the mid of the city.

Workers and employees who can afford their own transportation and rent are settled around the business hub. The second zone consists of offices and factories, industrial warehouses and transportation hub.

Third zone comprises of the typical residential houses. Mostly working class resides in this third zone. Fourth zone is also another residential area for elite and white collar job holders.  

Concentric zone model theory suggested that cities grow in a circular fashion.

Option D

Explanation:

First model that explained the inner structure of social setting in urban area arranged in a circular or series of rings is the concentric zone model. This model essentially proposes that the growth of the city starts from the centre and slowly it starts growing outwards in series of concentric circles or rings.  

This model has been criticised on the ground that it doesn’t apply universally rather it is more restricted to the cities in U.S. Even the new cities which are growing currently are not growing in accordance with this model.

world bank is the correct answer.

the density would be a smaller number.