单选题 .  People's tastes in recreation differ widely. At a recent festival of pop-music in the Isle of Wight, crowds of teenagers flocked to listen to their favorite singers and musicians. They went with single railway tickets and slept in the open, a very risky thing to do in the climate of Britain, even in August. They were packed together like sardines (沙丁鱼) for four days. There were innumerable thieves, a gang of roughs tried several times to break things up, and police were everywhere. At the end of the festival many young fans found themselves broke, with no money left, and they had difficulty in getting back home. Most people would consider these conditions a nightmare of discomfort; the fans appeared to enjoy it all enormously.
    Even in the overcrowded United Kingdom there are large tracts of open unspoilt country, where people with more traditional tastes can go for quiet, and for the sense of freedom they derive from contact with nature. In the national parks especially, modern development of housing and industry is strictly controlled. Visitors may walk for miles through landscape of the greatest beauty and wildness, and often of considerable historic or scientific interest. Along the coasts of some of the maritime counties, public pathways have been created; these paths stretch for many miles along cliffs that look out on the Atlantic Ocean or the English Channel. Another path, lying inland, goes along the range of mountains in the north of England. It is called the Pennine Way. Here, the long-distance walker and the nature-lover can find much to enjoy, without feeling disturbed by large numbers of their fellows.
    Yet few people make full use of the national parks established for everyone's benefit. The commonest thing nowadays is for family groups to motor out to a beautiful spot and park their cars in a lay-by (英国的路旁停车带). A picnic basket is produced, along with a folding table and chairs, a kettle and a portable stove. They then settle down to a picnic in the lay-by beside the car. Apparently their idea of enjoyment is to get into the fresh air and amongst the country sights and sounds without having to walk a yard. They seem almost to like to hear and to smell the traffic.1.  For the British, it is unsafe to ______.