单项选择题

TEXT E
The Pony Express
In the United States today, we can send a letter from coast to coast in just a few days for well under half dollar. But news did not always travel as fast or as cheaply as it does today, In the mid 1800s, trains and horse-drawn coaches carded mail. It took many weeks for news to travel from Now York to California.
In 1860, the railroad and telegraph reached only from the East Coast to Missouri, less than halfway across the coun try. Horse-drawn coaches, which were very slow, then carried the mail from Missouri to California, In April 1860, the Pony Express began to carry the mail from St. Joseph, Missouri, to Sacramento, California. The trip took just ten days -- half the time the coaches took.
The Pony Express was a horse relay system. There were stations every 10 or 15 miles along the route, which was nearly 3,200 kilometers’(2,000 miles) long. Fresh horses were at each station. The riders, with their heavy mailbags, changed horses at every station. They continued riding full speed for a total of about 100 miles. Then another rider look over and continued riding.
The Pony Express riders rode through dangerous territory, including mountains, deserts, and Indian lands. Bad weather didn’t stop these tough riders, either.
They rode through rain, snow, sleet, and blizzards, both night and day. The riders, therefore, had to be both brave and strong. Some newspapers in 1860 carried this advertisement:
Wanted: Young, skinny, wiry fellows, not over 18. Must be expert riders, willing to risk death daily. Orphans preferred.
Most of the young Pony Express riders completed the ride successfully. Some of them even became famous for their courage and bravery during difficult rides. What did these young men get paid for their bravery Twenty-five dollars a week. And what was the cost of sending a letter by Pony Express Five dollars a half-ounce in 1860, then reduced to two dollars in 1861.
In October 1861, the telegraph reached California. The Pony Express disappeared after this and became a short but exciting chapter in American history.
According to the passage, the Pony Express riders ore ______.