7 . It is most likely that you have seen a train, it may have been passing through your town, or you might have even been     1     (luck) enough to ride on one. Trains are a cool way to travel.     2     (actual), the earliest trains were just a series of carts (老式马车) joined together,     3     ran along wooden tracks and were usually pulled by horses and even people.

Around 1775, steam was being experimented with as    4     source of power. And in the early 1800s, the steam engine was invented and used into the train. This made    5     (pull) goods easier and a lot faster. Thanks to the trains, people and products could    6     (carry) off to other locations. By around the 1860s, the idea of the train had spread to the United States. Here trains were being used to pull grain (粮食)    7     farms to factories. And soon wealthy people wanted to take the train all the way to the Pacific coast. Then two    8     (company), Union Pacific and Central Pacific Railroads,     9     (get) the right to take on this great task of laying the track. And it took over six years and many lives    10     (complete) the first transcontinental (横贯大陆的) railroad.