A、Cars, buses, and trucks. B、Highways built outside of the city. C、Traffic lights. D、Reducing the number of buses and trucks. C

Cities try’ to improve their transportation in order for cars, buses and trucks to travel easily in them. Large highways run through cities, so people can travel from their home to their job quickly. Also, to control the vehicles on the highways, cities have installed traffic lights. Two cities experimented with public buses to reduce the number of automobiles on the street. In Rome, passengers on the city buses did not have to pay for a bus ticket. In Stockholm, people paid a low price for a one-year ticket to travel on any bus, trolley bus, or train in the city. Finally, to increase the safety of people who walk, many cities have closed some streets to vehicles.