吴中东：专业英语四级考试听力考前预测试题

（5）The first trans-continental railroad

　　When the first trans-continental railroad was completed in 1869, native lands seemed even more desirable, and movement westward increased as industrialism spread. The railroads spurred America’s transformation from an agricultural economy, or one based primarily on farming, to an economy where capitalism, or private ownership of businesses, prevailed. Industry in America developed far more rapidly than it had in Europe. Factories and mills spread quickly throughout New England prior to the Civil War due to good supplies of natural resources such as iron and coal, and the ease of transporting finished goods along the many navigable rivers. This in turn lead to the building of more railroads and canals to handle the increased traffic.

(6)Mississippi river

　　Mississippi river is the largest and most important river in North America. It has played a central role in the exploration and economic development of the continent. Many cities and towns began along the Mississippi and continue to depend on the river for their economic base, because the river makes it possible for large vessels to use the river. About 282 million metric tons of freight is carried on the river each year. The most important cargoes on the river are items such as coal, petroleum products, sand, and grain. The Mississippi Valley has rich soils, formed by thousands of years of deposition by the river. It supports agriculture, especially feed grains and soybeans in the north and cotton and rice in the south. The upper valley once contained vast nutritious beds, which were the basis of an extensive fishery in the 19th and early 20th centuries, but these were severely exhausted and are no longer commercially significant.

（7）The Bald Eagle