Thirty years ago, most teenagers had bicycles, but now they are comparatively rare. 【B1】 , motor scooters (小型摩托车) are much more common, 【B2】 , this may seem a sign of progress but 【B3】 the change is not necessarily for the better. It is easy to see why young people prefer scooters. 【B4】 , they are much faster and do not require much physical effort; 【B5】 , you can take a passenger with you on the pillion (后座) seat behind; 【B6】 , they give young people a feeling of independence, because they can travel further and impress their friends. 【B7】 , the disadvantages are equally obvious, 【B8】 first sight, scooters are more expensive to buy and to maintain, and 【B9】 . Those under 16 are not allowed to have them. 【B10】 , greater freedom brings danger because speed encourages young people to take risks and as a result scooters are involved 【B11】 more accidents, and the accidents are 【B12】 more serious. Bicycles are safer and easier to control. Years ago, teenagers had more experience with them because they 【B13】 to ride as young children, and consequently knew what they were capable of. 【B14】 , many young people overestimate what a scooter can do and pretend it has the power of a motor—cycle. 【B15】 , the fact is that bicycles are not very safe , 【B16】 ,in cities these days because there are more cars and drivers are not used to them and do not make allowances for them. 【B17】 , those who are old enough to ride scooters naturally prefer them. Those who are too young or cannot afford to buy a scooter probably find bicycles slow and uncomfortable 【B18】 , and riding bicycles requires 【B19】 experience of traffic than before. On balance, the change has been for the worse, 【B20】 for the 13—and 14—year—olds, but the only safe solution would be to have special lanes (车道) for cyclists. 【B1】