Although parks of all sizes and types exist at any level, the national parks, in particular, tend ____1____ (catch) our attention because of their large size and variety. They are ____2____ (treasure) of American heritage (遗产). How did the national park system come about? On a cool, starry night in mid-September 1870, four men relaxed before a campfire along the Firehole River in ____3____ is now northwestern Wyoming. They ____4____(be) part of a 15-member exploring party that had spent almost five awesome weeks in witness of the natural beauties there.

What should ____5____(do) with such a beautiful place? They wondered out loud. This area, with ____6____ (it) unique and breathtaking natural beauty, must be well preserved ____7____ all people of the nation to enjoy — as a national park. They all agreed and vowed (承诺) to promote the idea at the ____8____ (complete) of their journey. Their promotional work paid off. Two years later, 18 years before Wyoming became a state, Yellowstone became the first national park in the United States and the world. Yellowstone was the ____9____ (large) United States national park — 2.2 million acres — until Wrangell-Saint Elias in southern Alaska, _____10_____ became a national monument in 1978, took the honors as a national park in 1980 with 12.3 million acres.