Answer :
A A positive feedback loop involving the migration of goods and services away from an urban center
Step-by-step explanation:
Urban blight or urban decay(a sociological process) that occurs when a city or part of it falls into decrepitude and as such could encourage migration from there
It results from different causes or combinations of inter-related socio-economic conditions such as the city's urban planning decisions tight rent control or general economic problems ,the poverty of the local populace etc.