How did elevated trains and subways improve urban transportation? a). by using horses and carriages to commute b). by making the automobile unnecessary c). by transporting commuters without crowding city streets d). by delivering fresh food to people in cities

I believe the correct answer is C. by transporting commuters without crowding city streets.
Subway is found underground, which means that any type of transport provided underground will not affect the streets above. This is an important achievement of modern societies because it has prevented the creation of crowded streets and thus made it easier for people to get to places faster.

By transporting commuters without crowding city streets