Years ago our cities were full of cars,buses and trucks．Now the

Years ago our cities were full of cars,buses and trucks．Now the streets are completely congested(拥挤的)and it is very difficult to drive a car along them．Drivers must stop at hundreds of traffic lights．What are our cities going to be like in ten or twenty years?Will enormous(巨大的)motorways be built across them?With-big motorways cutting across them,full of noisy,dirty cars and lorries,our cities are going to be awful places．How can we solve the problem? There are some good ideas to reduce the use of private cars．In 1989,for example,the authorities in Rome began an interesting experiment:passengers on the city buses did not have to pay for their tickets. In Stockholm there was another experiment:people paid very little for a season ticket to travel on any bus,trolley bus,train or tram in all the city. In many cities now some streets are closed to vehicles,and pedestrians are safe there. In London there is another experiment:part of the street is for buses only,so the buses can travel fast．There are no cars or taxies in front of them. In many cities pedestrians are now much safer because__.
A、no traffic is allowed on some streets
B、traffic is computer-controlled
C、cars move very slowly
D、only one way streets are open to traffic
【正确答案】：A
【题目解析】：答案解析：根据文章内容，文中提到“在许多城市中，一些街道现在禁止车辆通行，行人在那里很安全。”这表明在这些特定的街道上，没有交通流量，因此行人可以更加安全。所以选项A“一些街道上禁止交通”是正确的答案。