资料题：Teenagers tend to have strange clothes and hairstyles because they（　）。

Voluntary Service Overseas (VSO) is a registered charity dedicated to assisting developmentin the world's poor countries. It is an independent non - sectarian organization. VSO is a direct response to an urgent need. Each year about 450 volunteers are sent to work on projects in 36 developing countries. Each volunteer goes overseas in response to a specific appeal from a developing county. Over the past 23 years more than 20, 000 volunteers have worked abroad with VSO. Together they have contributed over 30,000 man - years to development.But VSO volunteers gain as well as give. They gain responsibility, experience and a personal viewpoint on development debate. About all, VSO is aid that the Third World needs. For this reason "the Third Wald countries themselves pay almost half the cost of each VSO volunteer.When VSO was established over 20 years ago, the first volunteers were school-leavers. However, increasingly the demand was for skilled and professional people. Today, all VSO volunteers are skilled and/or qualified people-teachers and doctors, mechanics and electricians, accountants and civil engineers. Why do they volunteer? To make a personal contribution, to take on extra responsibility, to gain overseas work experience, to work within a community - of-ten for all these reasons. The task of VSO is to match these specialists with particular vacancies ,notified to them by overseas countries. Then having made the match, they prepare the volunteer to work for two years in a very different environment.