Final answer:
The concept that explains the changes in Oak Street is gentrification, which involves the transformation and revitalization of a neighborhood, usually leading to reduced crime but potentially displacing lower-income residents.
Step-by-step explanation:
The concept that best explains the change in Oak Street from a high-crime area to one of the safest areas in the city is gentrification. This involves the transformation of a neighborhood by buying and renovating properties, leading to an influx of middle-class or higher-income residents, which can displace the original, typically lower-income, inhabitants. The revitalization efforts described, such as remodeling row homes and encouraging residents to become homeowners, followed by community engagement through meetings and neighborhood watches, fit the model of gentrification, which often results in reduced crime and improvements in neighborhood amenities. It is important to note that while gentrification can improve safety and aesthetics, it may also lead to displacement and cultural shifts that can affect the existing community.