Hi!
The answer would be D, urban flight.
Step-by-step explanation
If we go over the terms then you'll be able to understand this better
Zoning: The act of dividing a town or piece of land into areas for development purposes.
Urban planning: The study and action of dealing with the growth and functioning of cities and towns.
Urbanization: The increase of population in cities and towns versus rural areas
Urban flight: the name given to the process in which people left the cities and moved to the suburbs.
With these terms, you can see the correct term that would be given to the Richardson family leaving the city for the suburbs would be urban flight, because as the name explains it, they are fleeing the urban chaos.