Curitiba, Brazil, Has Shown Us That ______________

Curitiba, Brazil, has shown us that ______________.

A) prohibition of motorized vehicles in urban reduces pollution and saves energy
B) once roads are widened, traffic congestion decreases
C) traffic flows smoothly once pedestrians and bicycles are eliminated
D) a walkable city center and expanded bus system can solve a large city's traffic congestion
E) unregulated urban sprawl produces severe air pollution