Travelers have camped and used packs for centuries. In 1914, the word “backpack” in relation to a travel pack first __31__ (appear) in America. Now backpacking is a popular outdoor activity. Backpacking involves hiking to a camping place. Hikers always carry packs __32__ contain food and necessary items. Backpacking usually involves at least one night of outdoor camping, and can last for months if hikers add to __33__ supplies along the way. Many __34__ (mountain) regions of the world are popular among backpackers.
Backpacking is __35__ (usual) done in groups of two or more, __36__ some backpackers will go hiking alone. __37__ (Depend) on the physical stress of the trip, people of most levels of fitness can take part in backpacking.
Some individuals use backpacking __38__ a method of travel, especially in Europe. Backpacking is a cheap and fun way to __39__ most parts of Europe. Traveling backpackers appreciate the convenience. __40__ is also a way to network (建立联系) with a wide variety of individuals who meet in the course of traveling.