题目内容
A．makeB．getC．possessD．select
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The National Park Service
America's national parks are like old friends. You may not see them for years at a time, but just knowing they're out there makes you feel better. Hearing the names of these famous old friends--Yosemite, Yellowstone, Grand Canyon--revives memories of visits past and promotes dreams of those still to come.
From Acadia to Zion, 369 national parks are part of a continually evolving system. Ancient fossil beds, Revolutionary War battlefields, magnificent mountain ranges, and monuments to heroic men and women who molded this country are all a part of our National Park System (NPS). The cafe and preservation for future generations of these special places is entrusted to the National Park Service. Uniformed Rangers, the most visible representatives of the Service, not only offer park visitors a friendly wave, a helpful answer, or a thought-provoking history lesson, but also are skilled rescuers, firefighters, and dedicated resource protection professionals. The National Park Service ranks also include architects, historians, archaeologists, biologists, and a host of other experts who preserve and protect everything from George Washington's teeth to Thomas Edison's wax recordings.
Modern society has brought the National Park Service both massive challenges and enormous opportunities. Satellite and computer technologies are expanding the educational possibilities of a national park beyond its physical boundaries. Cities struggling to revive their urban cores are turning to the Park Service for expert assistance to preserve their cultural heritage, create pocket parks and green spaces, and re-energize local economies: Growing communities thirsty for recreational outlets are also working with the NPS to turn abandoned railroad tracks into bike and hiking trails, as well as giving unused federal property new life as recreation centers.
To help meet these challenges and take advantage of these opportunities, the National Park Service has formed partnerships--some dating back 100 years, some only months old--with other agencies, state and local governments, corporations, American Indian tribes and Alaska Natives, Park Friends groups, cooperating associations, private organizations, community groups and individuals who share the National Park ethic.
National Park Week 1996 is a celebration of these partnerships.
Why are America's national parks like old friends？
A．so thatB．in thatC．considering thatD．by reason that
外部性的存在意味着边际社会成本小于边际私人成本。
所有的Nash均衡同时也是占优策略(dominant strategy)均衡。
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