In the past, the Park Service focused on making the big scenic parks more 【21】______ and comfortable for tourists. Roads were paved to allow 'windshield visitors' to experience the grandeur of nature without leaving their cars, and a 【22】______ number of hotels and grocery stores were permitted to open 【23】______ the park boundaries. Now this trend is changing. Plans have been made to 【24】______ the parks to their natural condition as much as possible. The objective of such a move would be to secure the preservation of the parks for future generations, 【25】______ allowing present-day visitors to experience pure wilderness, 【26】______ from any obvious signs of civilization -- an opportunity which is quickly disappearing in the twentieth century. 【27】______ plans call only 【28】______ a reduction in the number of cars 【29】______ into the parks each day, but 【30】______ , tourists may have to leave their cars at the gates and then either visit the park on foot 【31】______ use park 【32】______ 【33】______ , stores and hotels may no longer be allowed within park boundaries and even the number of campgrounds may be restricted. Denali National Park in Alaska serves as an excellent 【34】______ for this new type of park, one which has been changed only slightly from its 【35】______ state. There is only one road, unpaved in 【36】______ , which cross 【37】______ Denali. As car traffic is strictly limited, many visitors experience the magnificent 【38】______ and wildlife from a park bus. There are no hotels or stores and only seven campgrounds within Denali's 3,000 square miles. This 【39】______ isolation offers backpackers, canoeists, and other sport enthusiasts a 【40】______ physical and psychological challenge. 【21】