题目内容：
根据以下资料，回答题： In the past，the Park Service focused on making the big scenic parks more___21___and comfort-able 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 3l 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．calloe—ists，and other sport enthusiasts a___40___physical and psychological challenge．
A．possible
B．accessible
C．approachable
D．reachable
参考答案：
答案解析：