A river empties into the ocean; the density of ocean water

Sandra lives in the heart of a large city. lately, there have been robberies on several of the streets near where sandra lives but none on her street. sandra and her neighbors believe that they have not seen any crime on their street because they know each other, notice when strangers or strange cars are in the neighborhood, and have a mix of old retired couples and young families who use the neighborhood at different times of the day. jane jacobs would see this as an example of: