阅读理解。 Except for the Indians, the earliest backpackers in America were frontiersmen (边疆居民), who walked in the wilderness looking either for necessities such as food and water or for sources of wealth such as fur and gold. For them backpacking was a way of survival or a means of achieving what one day would be called the 'American dream'. Today, however, many people enjoy backpacking as a recreational activity. Shouldering a pack and leaving behind the world of telephone, television and traffic promise an exciting experience. Testing one's stamina (耐力) and skills and challenging a sense of one's place in the natural world can be rewarding. Moreover, backpacking is an activity that can last any length for time and can be enjoyed alone or with friends. Then too, a backpacking trip may be organized within a day or two. The backpacker and his friends have only to decide on their destination and then organize the all-important kit (工具包), whose contents they must depend on throughout their trip. A map, a compass, a flashlight, along with first-aid equipment, food, and extra clothing can be rounded up without much difficulty. Once the backpackers have left word about where they go in a note on the refrigerator door or in a message on an answering machine, they can look forward to an adventure that will lift the spirit and encourage the soul. Their outing will enable them to return in a short time to the age of technology with the courage and independence of Natty Bumppo, who did indeed belong to the age of the frontier. 1. The passage mainly discusses _____. [     ] A. the early backpackers B. how backpacking started C. important tips on backpacking D. why people of today are interested in backpacking 2. According to the passage, the early backpackers _____. [     ] A. had no recreation in life B. did backpacking for a living C. enjoyed backpacking very much D. had better skills than backpackers today 3. It seems that the writer of the passage thinks that backpacking today is _____. [     ] A. a waste of time B. a great adventure C. a rewarding experience D. a means to achieve American Dreams 4. One of the advantages of backpacking is that _____. [     ] A. it is not so challenging as other activities B. it can help people to establish a link with nature C. it does not require people to decide on a destination D. it is a group activity and can cure a person's loneliness